- 04 Mar 2018
Have you ever listened about the “Second Brain”?
Yes, you have! whenever you are told to trust your gut instinct. This brain and gut connection is not just metaphorical. An extraordinarily extensive network of neurons (more than 100 million neurons) lines our gut that scientists have named it the Second Brain.
What about the inhabitants of gut including good and bad microbial flora?
Gut microbiota weighs up to 2kg containing trillions of micro-organisms. One-third of these microbiotas is common to all people while others are specific to every individual’s gut depending on the type of diet they take in and their lifestyle.
“Gut flora is a complex community of organisms that inhabit human and animal digestive system”. Relation between humans and gut flora is mutualistic. Bacteria in the digestive system assist in nutrient metabolism, vitamin production, and waste processing. They also aid in the host's immune system response to pathogenic bacteria.
Healthy Microbiota & Healthy Brain
The gut has a bidirectional relationship with the central nervous system referred to as the “gut-brain axis”. Introduction of good bacterial strain reduces anxiety and stress level. Gut-brain axis is used by bacteria to affect the brain function. The most significant factor related to the health of microbiome -- thus, brain – is healthy food. Following are the positive influencing microbiota Lactobacillus that produce lactic acid are found in yogurt. Taking in yogurt will boost mental capacity and relieve stress, it also aids in digestion and relieves constipation. But make sure yogurt is live culture (probiotic). Bifidobacteria feast on chocolate and ferment it causing positive effects on our health and body. Dark chocolate is also very beneficial for the heart because bacteria (Bifidobacterium, LAB, yeast) ferment it into healthful anti-oxidants. Prebiotic foods including raw garlic, raw, and cooked onions allow the healthy microbiota to grow and thrive while inhibits the growth of non-healthy microbiota. Environmental toxins can disturb microbiome and have adverse effects on brain health to save ourselves from these effects, use of home filtered water should be made compulsory. Such filters should be used that remove harmful toxins like chlorine. Fermented foods like pickles, kefir, kimchi etc. are the source of Lactobacillus lactis species and defend against leaky gut. These were some healthy microbial flora and their sources having a positive effect on your body and brain.
Non-Healthy Microbiota & Whacky Gut
There are bidirectional links between stress and microbiota. Irritable Bowel Syndrome (IBS) and Chronic Fatigue Syndrome (CSF) are also related to the gut microbiota. In CSF patients there is an alteration in normal microbiota resulting in symptoms as depression, neurocognitive impairment, pain and sleep disturbance. While IBS is considered as a gut-brain disorder which is worsened by stress. Researchers are investigating whether these unhealthy microbiota resulting in IBS are also the cause of mood disorders. No bacteria can be inherited as bad, when our body is out of balance it takes advantage and proliferates. Some bacteria having a bad reputation are given below Microbial imbalance as a high level of Lactobacillus can also cause mood disturbance and sleep disturbances. Staphylococcus can cause food poisoning, it can be found in unpasteurized milk and can affect when hygiene is poor. Higher levels of the bad clostridium bacteria can cause fatigue by using bidirectional gut-brain axis. By eating junk food firmicutes and bifidobacteria level falls and there is a rise in the level of bacteroidetes causing the lethargic behavior to upshot and immunity problems set in.
Healthy Gut of a Baby
It is believed that when babies are born their guts are sterile, as soon as they encounter the genitourinary tract and mother’s skin, they are exposed to microbial flora. Microbial flora is important to develop in infants or babies for normal functioning. This healthy microbial flora to a baby is also provided by mother through breastfeeding. Milk is a cocktail of healthy microbiota and immunoglobulins causing development and growth of microbial flora in infant’s gut. So it is necessary for mothers to take healthy balanced diets rich in probiotic, prebiotic and fermented foods.
Due to the increased demand for fruits and vegetables, portals like Selly.pk offer a much feasible way of shopping. It takes a lot less effort to buy fruits and vegetables online.
Selly.pk is a welcome initiative if you ask me because the streets and roads are already piling up with fruit & vegetable vendors. More people should realize similar ideas. However, this can be depressing for those conventional vendors if the people start buying online sabzi in Lahore. The status quo always works against change but because this is a good change, we should all work together to make it a successful prospect.
Selly.pk Doing Business with Morals
Fruit market Lahore receives new rates of fruits & veggies daily. In order to comply with a standardized rate, Selly.pk is in touch with fruit officials who know this industry on fingertips. This only gives it an upper hand over the common vendors who are more interested in earning high profits rather than being civil and selling products at a decent price.
In the fruit & vegetable market, the Jin of inflation is still under control but as soon as those items reach private vendors in different localities, the price starts touching the skies. Fruit price in Pakistan should have checks & balances so the vendors can’t get greedy.
Your Online Partner
Selly.pk is one of a kind online fruit shop in Lahore. There are not many online fruit shops in Pakistan, therefore, this is a healthy and productive initiative. Where to order fresh vegetables online? How many of us haven’t thought about this question? It is time, a serious response came through and it has in the form of Selly.pk.
Price Comparable to the Average Market Price
It is a pioneering name regarding online fruit and vegetable shopping. Moreover, one would think the price would be higher because it is online. No, not at all. I do most of my shopping from Selly.pk and the online vegetable rates are lower than most vendors out there.
Every household has a need for a fresh supply of fruits and vegetables daily. Online vegetable shopping is much more time-saving because lives are getting busier every day. It is not easy to stop the car on your way back home from work and buy fruits or vegetables.
Fixed Reasonable Rates – Bargaining Not Required
There is no need to overexert yourself anymore with Selly.pk in town. Online vegetable shopping is simpler rather than spending your brains in bargaining with the vendor at the end of the street. Moreover, the call representatives taking your call are very well-behaved, often stating the list of items to make the selection process easier for you. As soon as you place an order for fresh vegetables online, the processing starts and they promise you to reach within 45 minutes. In my case, they have always been on time. They have met my expectations so far delivering high-quality fruits and vegetables to my doorstep.
Call at your Convenience
Some of us may have trouble ordering through the website due to the fact some of us aren’t technical enough. But you can always call on 0304-111-7355 to place your order.
How Can We Pay?
Cash on delivery is encouraged because we can’t pay by debit or credit cards on the website. Neither is there a card reader with the rider to swipe those cards. These two procedures are something that is lacking in the current order of things.
The riders delivering the goods speak to you in a polite tone without being aggressive or suddenly getting rude.
They have openly declared their return policy. We can instantly return stale fruits or vegetables at the time of delivery and no questions, whatsoever, will be asked.
Fruit and vegetable grocery list – it doesn’t matter how long the list is, Selly.pk is always up for the task delivering them on time. Fresh fruit for sale online, especially in winters is more like a blessing because it’s too cold to go out for shopping anyway. Buy vegetables online easily through Selly.pk because the website is superb. Just keep on tapping the items you want to buy and keep adding them to cart until you are ready to check out.
Fresh vegetables for sale at this website are packed in a luxurious way, unlike those cheap plastic bags we normally see at shops, with a symbol or monogram of Selly.pk attached to each packet.
The Gist of the Matter
Selly.pk provides fresh vegetables near you if you are in Lahore. However, one can consider it as a fresh vegetable market nearby with so many choices to choose from. You only need a working smartphone with an active Wi-Fi connection or mobile data connection. Type in Selly.pk in your browser and you are good to go. Fresh fruits and vegetables delivered to your doorstep in a matter of minutes. Shopping was never so convenient before!
- 11 Feb 2018
Torsion is a process in which the viscero-pallium rotates anti-clockwise through 180° from its initial position during larval development. So that the mantle cavity, with its pallial complex, is brought to the front of the body in the adult.
How Torsion Occurs
Torsion is not an evolutionary hypothesis. Its occurrence can be seen during embryogeny of living gastropods. Before torsion the larva is quite symmetrical, the mantle cavity is backward and downward, the alimentary canal is straight and anus opens posteriorly in the middle line. The shell and visceral mass originally saucer-shaped, which is first cone-shaped and then spirally coiled. When the shell lies dorsally and forms a coil anterior side then the shell is called exogastric.
The ventral flexure is followed by a lateral torsion, so that the dorsal or exogastric shell becomes a ventral or endogastric shell. The entire process takes 2 to 3 minutes as in Acmaea.
Torsion is actually effected due to the contraction of the larval retractor muscles, in which only the narrow neck of the larva is actually twisted. So the everything between the head and the anus undergoes an anti-clockwise rotation at the angle of 180°.
Thomson (1958) described five ways by which the torsion can be brought about.
- In Archaeogastropods, the Acmaea, the torsion takes place by muscles contraction alone.
- The rotation of 180° is completed in two stages, the first movement takes place by the contraction of larval retractor muscle and second rotation is slower by different growth. It is very common as in Patella, Haliotis etc.
- The rotation of 180° takes place by only differential growth processes like Vivapara.
- Rotation by differential growth processes, with anus coming to a position appropriate to the adult state like Aplysia.
- Torsion is no longer recognizable as a movement of viscera-pallium, the organs in the post-torsional position from their first appearance as in Adalaria.
Effects of Torsion
The effect of torsion first time indicated by Spengel in 1881. The effects are not equally examined in all the gastropods by the general effects are described as follows:
- Displacement of mantle cavity: The mantle cavity was primarily present on the posterior side. The elongation of the ventral foot which was primarily very small. After torsion, the mantle cavity opens just behind the head and its associated parts are shifted forwards.
- Changes in relative position: Before torsion, the anus, ctenidia and excretory opening were placed on the posterior side and the auricles were placed behind the ventricle but after torsion the anus, ctenidia and excretory opening become anterior and the auricles lie in front of the ventricle. The original posterior face of the visceral sac becomes the anterior face so that the visceral organs morphologically of the original right side change into the left side.
- Looping of alimentary canal: The alimentary canal which was originally straight from mouth to anus, after torsion, it changes into a loop.
- Chiastoneury: The long, uncoiled pleuro-visceral nerve connectives become a figure of "8" after twisting. The right connective with its ganglion passes over the intestine to form the supra-intestinal connective, while the next connective pass under the intestine to form the infra-intestinal connective.
- Endogastric coil: The coil of visceral sac and shell, which was primarily dorsal or exogastric become ventral and endogastric after torsion.
- Loss of Symmetry of Atrophy: The anus changes their original position towards the right side of the pallial cavity so that the original symmetrical condition disturbed.
The torsion is reversible in Eu-thy-neura and its reversal is known as detorsion by which animal become untwisted and symmetrical.
- 06 Feb 2018
The “pearl” is literally formed by the mantle epithelium, which becomes deposit around any external body or particles, these external particle or body invade in between the shell and mantle in any way.
Pearl is secreted by the mantle as a means of protection against a small external particle. When an external particle or body, such as a grain of sand or a small parasite invades in between the mantle and the shell it becomes enclosed in a sac of mantle epithelium which produces irritation. The irritation stimulates the mantle epithelium to secrete thin concentric layers of mother of pearl around the foreign body. The amount of deposition is in direct proportion to the degree of irritation. After several years, a pearl will be formed, usually, it requires 3 to 4 years to produce a pearl of considerable size but a large pearl requires about 7 years. The foreign particles in the pearl are called nucleus whereas the thin nacre layers are concentric and called the mother of pearl.
Pearls are formed by various clams and oysters, but those produced by the marine pearl oysters, Meleagrina of Eastern Asia are the most valuable.
- 30 Jan 2018
Blackheads are the most common problem in the majority of people. This problem arises when the oily secretion of the sebaceous glands forms a blockage in your skin pores. When the oil is exposed to air, it oxidizes and turns into black and forms blackhead. So the question is that how you can remove blackheads from your skin.
Removing of blackheads from your skin is very simple and you can do this at home, all you need to do is remove the entire blockage from your skin pores.
In order to remove the blockage from your skin pores, you need the following material.
- Towel or soft cloth
- Blackhead removal strips or pads
- Salicylic acid (C7H6O3)
Wash your skin with the slightly hot water, and gently compress your skin pores with the help of towel or soft cloth. The warmth will open the pores of your skin and make it easier to remove the blockage caused by secretion of the sebaceous glands and to get rid of blackheads. Follow this step upto 5 times.
Apply a blackhead elimination strip or pad to your face while your skin pores are still moist from the compress done in step 1. The moisture to your pores and skin will help the blackhead removal strip cohere on your skin and blackheads. Allow 10 to 15 minutes for the blackhead removal strip to stick itself.
After 10 to 15 minutes, pull the strip off. It should remove the blockage and blackheads from your skin pores in a different level of success. But in some cases, it removes the entire blockage and blackheads; in other situations, only the head of the blockage is ripped from the pores of the skin.
With the help of your fingertips, squeeze your skin gently to remove the blackheads from your skin. Note that fingernails should not be used for that purpose as it may harm your skin. If they do not pop out effortlessly, do not squeeze harder as it may harm your skin. Rather, try making use of warmth compress and squeezing another time straight away after removing the warm compress.
If the blackheads do not pop out by this method, they probably cannot be removed adequately with your fingers.
Salicylic acid (C7H6O3) is a medication most commonly used for the skin treatment. It removes the outer layer of the skin and most commonly used for the treatment of calluses, dandruff, acne, ringworm, warts, psoriasis and ichthyosis.
Apply a thin layer of salicylic acid liquid or paste onto your skin and leave it for a minute. After the use of salicylic acid, do another hot compress and try to squeeze out the remaining extra blackheads.
MODE OF ACTION: When you apply the layer of salicylic acid liquid onto your skin, it breaks down the sebum oil and can get deep into your skin pores where your fingers cannot.
You can compare the deionized water vs distilled water, however, to mention that the distilled water is that the same as deionized water may be a mistake. The terms “distilled water” and “deionized water” are usually misunderstood. during this article, you'll notice the reason to grasp the variations and similarities of those 2 completely different water cleanup technologies.
The oldest technique for production of pure water is that the thermal technique or distillation – water evaporation from the surface and condensation. the premise of the method is that the transfer of water within the vapor section with its later condensation. the most downside of this technique is that the terribly high maintenance prices of the electricity required to convert the water into the steam. additionally, within the method of steam formation in conjunction with water molecules, alternative solutes will enter the steam in keeping with their volatility. Evaporation is achieved in varied ways: the vacuum on top of the water, heating, etc.
Let’s contemplate the distillation. What’s happening within the method of distillation? The water molecules have the boiling purpose of 100°C or 212° F. alternative substances have completely different boiling points. The substance that boils at a lower temperature evaporates initial. The boiling purpose of assorted impurities is higher, and, in theory, they're going to begin to evaporate, once the water has already cooked out. The substance that boils at a lower temperature evaporates initial. because of this distinction the water is separated.
As a result, in theory when the distillation the fully pure water is obtained. Actually, organic substances, that have the similar boiling purpose than that of water will supply the water. let's say if the water contains the oil drops they will be found additionally within the liquid. There area unit much no salts within the water, as a result of the salt boils at a far higher temperature. To eliminate the matter of organic substances, the water distillers have pre- and post water filters.
The absolute advantage of the water is that the complete absence of harmful substances.
REVERSE OSMOSIS (RO) WATER
The latest various to the thermal technique for getting of water may be a two-stage reverse diffusion. The technology relies on the double passage of raw water through a tissue layer beneath the pressure. As a result, water is split into 2 streams: the filtrate (purified water) and concentrate (a targeted resolution of impurities). The two-stage reverse diffusion system will considerably cut back operational prices and improve the standard of obtained water. The reverse diffusion water treatment technology is that the most typically employed in households and within the trade for preparation of drinkable.
DEIONIZED (DI) WATER
Deionized water is deeply demineralized, ultrapure water with the impedance on the point of eighteen megohm-cm. it's employed in electronics, computer circuit boards, instrument manufacture, pharmacy, laundry liquids, etc.
In order to get the top quality pure deionized water, a multi-stage water purification method is used. when pre-cleaning, the water is equipped with the reverse diffusion membrane, so the water is filtered through a special deionization medium, that removes the remainder of the ions from the water. The purity of deionized water will exceed the purity of water.
SIMILARITIES AND DIFFERENCES: DISTILLED WATER Vs RO WATER Vs DEIONIZED WATER
|DISTILLED WATER||REVERSE OSMOSIS (RO) WATER||DEIONIZED (DI) WATER|
|Distillation is employed in the main in laboratories and factories, wherever it's required. Reverse diffusion is widely employed in water treatment plants, each reception and for the manufacture of assorted drinks, drinking water, etc.|| ||DI water is as pure because the water or maybe purer|
Distillation, RO and deionization processes are supposed to purify the water of the contaminants: mercury, lead, strontium, nitrates, phosphates, manganese, in addition, pesticides.
- 17 Jan 2018
Diabetes is epidemic; there is barely any family left that does not have a member diagnosed with diabetes. In urban areas, almost one-tenth of people have diabetes, and at least one-third are at risk of developing it soon if they do not do something about it. That means if not diabetic, every family surely has someone with prediabetes.
Diabetes is primarily caused by faulty lifestyle, followed for years, wrong kind of diet, absolute lack of exercise, and chronic stress, and low interaction between family members are all contributors to it.
Diabetes differs from all the other diseases in a way that it is infectious by lifestyle instead of microbes. Meaning a particular kind of lifestyle seems to prevail within the family. Finding an only single obese person in a family is rare. Similarly, if one is not doing exercise in the family, probably none is doing it.
The family is intended to function as a single entity, but not in negative direction, thus by changing the course of lifestyle by motivating and helping each other, whole family can benefit.
However, it seems that families are not discussing much diabetes, exercise, stress, and emotional problems.
“They say they care, but they rarely help, participate or motivate, they do not seem to understand me” is the most common complaint of people about their family members and close friends. In fact, some research shows that often friends are helping and providing more emotional support than the family members.
Although we all expect greater emotional support from family members, lack of such support may have reasons like little time or other lifestyle issues.
Can family support indeed make a difference?
At least all the research, hundreds of them, seems to support the idea that family support can make a huge difference. As we already mentioned that particular kind of lifestyle is prevalent in the whole family.
Whether it is a preference for specific type of food items, going out, meeting friends, doing exercise, spending leisure time, everything needs to be changed in diabetes, and perhaps everyone in the family has to change a bit. Wouldn’t it be best to work as a team? Instead of individual efforts. Sharing experience, motivating, has indeed shown to make efforts more successful.
Research has shown that adherence to exercise and medications are much better when done with the family support. Married people usually have higher compliance rate, though that cannot always be said about the lifestyle changes. People with families may exercise less as compared to those living alone.
Isn’t a family all about emotional support, love, help? Principally it must be the case, though in reality things often differ.
Thus for better diabetes management, prevention, it is vital that the whole family participates, and the process does not have to be boring. Supporting each other should be converted into a game, a fun, something to be enjoyed, something that brings emotional happiness to all the participants.
Iron sharpens iron; humans are not made to be left alone. They always psychologically feel better when they are continually communicating, when they are loved and praised. Modern technology has made us busier than ever; we are spending more time in unnecessary communication at the cost of neglecting the necessary one.
Thus the solution to the problem created by the technology should also be sought in technological advancement itself.
Why not start using an app that is made explicitly for members of the family, instead of social apps that are more open, and less focused on interaction at the family level.
An app called CricleCare is explicitly made to fulfill that gap. It is a fun way to keep you close friends and family members motivated. It is different in a way that it has been created to improve the communication between the small and closed circles. It has all the tools to make that conversation more relaxed and fun. So you can exchange messages, send stickers. Most importantly, you can encourage the family members by giving batches. Thus you can provide batches to kids for being good at home, doing all the tasks. Give batches for keeping up with exercise, reminding to take medicine, and much more. It has many features of health app like counting steps, providing information about burnt calories. However, unlike the traditional health apps, it is also about the involvement of the whole family. It merges the benefits of health app and family support platform.
- 28 Sep 2017
Total serum thyroxine includes both free and protein-bound thyroxine and is usually measured by competitive immunoassay. Normal level in adults is 5.0-12.0 μg/dl.
Test for total thyroxine or free thyroxine is usually combined with TSH measurement and together they give the best assessment of thyroid function.
Causes of Increased Total T4
- Hyperthyroidism: Elevation of both T4 and T3 values along with decrease of TSH are indicative of primary hyperthyroidism.
- Increased thyroxine-binding globulin: If concentration of TBG increases, free hormone level falls, release of TSH from pituitary is stimulated, and free hormone concentration is restored to normal. Reverse occurs if concentration of binding proteins falls. In either case, level of free hormones remains normal, while concentration of total hormone is altered. Therefore, estimation of only total T4 concentration can cause misinterpretation of results in situations that alter concentration of TBG.
- Factitious hyperthyroidism
- Pituitary TSH-secreting tumor.
Causes of Decreased Total T4
- Primary hypothyroidism: The combination of decreased T4 and elevated TSH are indicative of primary hypothyroidism.
- Secondary or pituitary hypothyroidism
- Tertiary or hypothalamic hypothyroidism
- Hypoproteinaemia, e.g. nephrotic syndrome
- Drugs: oestrogen, danazol
- Severe non-thyroidal illness.
Free Thyroxine (FT4)
FT4 comprises of only a small fraction of total T4, is unbound to proteins, and is the metabolically active form of the hormone. It constitutes about 0.05% of total T4. Normal range is 0.7 to 1.9 ng/dl. Free hormone concentrations (FT4 and FT3) correlate better with metabolic state than total hormone levels (since they are not affected by changes in TBG concentrations).
Measurement of FT4 is helpful in those situations in which total T4 level is likely to be altered due to alteration in TBG level (e.g. pregnancy, oral contraceptives, nephrotic syndrome).
Total and Free Triiodothyronine (T3)
- Diagnosis of T3 thyrotoxicosis: Hyperthyroidism with low TSH and elevated T3, and normal T4/FT4 is termed T3 thyrotoxicosis.
- Early diagnosis of hyperthyroidism: In early stage of hyperthyroidism, total T4 and free T4 levels are normal, but T3 is elevated.
A low T3 level is not useful for diagnosis of hypothyroidism since it is observed in about 25% of normal individuals.
For routine assessment of thyroid function, TSH and T4 are measured. T3 is not routinely estimated because normal plasma levels are very low.
Normal T3 level is 80-180 ng/dl.
Free T3: Measurement of free T3 gives true values in patients with altered serum protein levels (like pregnancy, intake of estrogens or oral contraceptives, and nephrotic syndrome). It represents 0.5% of total T3.
Thyrotropin Releasing Hormone (TRH) Stimulation Test
- Confirmation of diagnosis of secondary hypothyroidism
- Evaluation of suspected hypothalamic disease
- Suspected hyperthyroidism
This test is not much used nowadays due to the availability of sensitive TSH assays.
- A baseline blood sample is collected for estimation of basal serum TSH level.
- TRH is injected intravenously (200 or 500 μg) followed by measurement of serum TSH at 20 and 60 minutes.
- Normal response: A rise of TSH > 2 mU/L at 20 minutes, and a small decline at 60 minutes.
- Exaggerated response: A further significant rise in already elevated TSH level at 20 minutes followed by a slight decrease at 60 minutes; occurs in primary hypothyroidism.
- Flat response: There is no response; occurs in secondary (pituitary) hypothyroidism.
- Delayed response: TSH is higher at 60 minutes as compared to its level at 20 minutes; seen in tertiary (hypothalamic) hypothyroidism.
Box 864.1 Thyroid autoantibodies
Various autoantibodies (TSH receptor, antimicrosomal, and antithyroglobulin) are detected in thyroid disorders like Hashimoto’s thyroiditis and Graves’ disease. Antimicrosomal (also called as thyroid peroxidase) and anti-thyroglobulin antibodies are observed in almost all patients with Hashimoto’s disease. TSH receptor antibodies (TRAb) are mainly tested in Graves’ disease to predict the outcome after treatment (Box 864.1).
Radioactive Iodine Uptake (RAIU) Test
This is a direct test that assesses the trapping of iodide by thyroid gland (through the iodine symporters or pumps in follicular cells) for thyroid hormone synthesis. Patient is administered a tracer dose of radioactive iodine (131I or 123I) orally. This is followed by measurement of amount of radioactivity over the thyroid gland at 2 to 6 hours and again at 24 hours. RAIU correlates directly with the functional activity of the thyroid gland. Normal RAIU is about 10-30% of administered dose at 24 hours, but varies according to the geographic location due to differences in dietary intake.
Causes of Increased Uptake
- Hyperthyroidism due to Graves’ disease, toxic multinodular goiter, toxic adenoma, TSH-secreting tumor.
Causes of Decreased Uptake
- Hyperthyroidism due to administration of thyroid hormone, factitious hyperthyroidism, subacute thyroiditis.
RAIU is most helpful in differential diagnosis of hyperthyroidism by separating causes into those due to increased uptake and due to decreased uptake.
An isotope (99mTc-pertechnetate) is administered and a gamma counter assesses its distribution within the thyroid gland.
- Differential diagnosis of high RAIU thyrotoxicosis:
– Graves’ disease: Uniform or diffuse increase in uptake
– Toxic multinodular goiter: Multiple discrete areas of increased uptake
– Adenoma: Single area of increased uptake
- Evaluation of a solitary thyroid nodule:
– ‘Hot’ nodule: Hyperfunctioning
– ‘Cold’ nodule: Non-functioning; about 20% cases are malignant.
Interpretation of thyroid function tests is shown in Table 164.1.
Table 864.1 Interpretation of thyroid function tests
|1. TSH Normal, FT4 Normal||Euthyroid|
|2. Low TSH, Low FT4||Secondary hypothyroidism|
|3. High TSH, Normal FT4||Subclinical hypothyroidism|
|4. High TSH, Low FT4||Primary hypothyroidism|
|5. Low TSH, Normal FT4, Normal FT3||Subclinical hyperthyroidism|
|6. Low TSH, Normal FT4, High FT3||T3 toxicosis|
|7. Low TSH, High FT4||Primary hyperthyroidism|
Neonatal Screening for Hypothyroidism
Thyroid hormone deficiency during neonatal period can cause severe mental retardation (cretinism) that can be prevented by early detection and treatment. Estimation of TSH is done on dry blood spots on filter paper or cord serum between 3rd to 5th days of life. Elevated TSH is diagnostic of hypothyroidism. In infants with confirmed hypothyroidism, RAIU (123I) scan should be done to distinguish between thyroid agenesis and dyshormonogenesis.
- 28 Sep 2017
|Box 863.1 Terminology in thyroid disorders |
Among the endocrine disorders, disorders of thyroid are common and are only next in frequency to diabetes mellitus. They are more common in women than in men. Functional thyroid disorders can be divided into two types depending on activity of the thyroid gland: hypothyroidism (low thyroid hormones), and hyperthyroidism (excess thyroid hormones). Any enlargement of thyroid gland is called as a goiter. Terminology related to thyroid disorders is shown in Box 863.1.
Hyperthyroidism is a condition caused by excessive secretion of thyroid hormone. Causes of hyperthyroidism are listed in Table 863.1.
Table 863.1 Causes of hyperthyroidism
Clinical characteristics of hyperthyroidism are nervousness, anxiety, irritability, insomnia, fine tremors; weight loss despite normal or increased appetite; heat intolerance; increased sweating; dyspnea on exertion; amenorrhea and infertility; palpitations, tachycardia, cardiac arrhythmias, heart failure (especially in elderly); and muscle weakness, proximal myopathy, and osteoporosis (especially in elderly).
The triad of Graves’ disease consists of hyperthyroidism, ophthalmopathy (exophthalmos, lid retraction, lid lag, corneal ulceration, impaired eye muscle function), and dermopathy (pretibial myxoedema).
|Box 863.2 Thyroid function tests in hyperthyroidism |
In most patients, free serum T3 and T4 are elevated. In T3 thyrotoxicosis (5% cases of thyrotoxicosis), serum T4 levels are normal while T3 is elevated. Serum TSH is low or undetectable (< 0.1 mU/L) (Box 863.2).
Undetectable or low serum TSH along with normal levels of T3 and T4 is called as subclinical hyperthyroidism; subtle signs and symptoms of thyrotoxicosis may or may not be present. Subclinical hyperthyroidism is associated with risk of atrial fibrillation, osteoporosis, and progression to overt thyroid disease.
Features of primary and secondary hyperthyroidism are compared in Table 863.2.
Table 863.2 Differences between primary and secondary hyperthyroidism
|Parameter||Primary hyperthyroidism||Secondary hyperthyroidism|
|1. Serum TSH||Low||Normal or high|
|2. Serum free thyroxine||High||High|
|3. TSH receptor antibodies||May be positive||Negative|
|4. Causes||Graves’ disease, toxic multinodular goiter, toxic adenoma||Pituitary adenoma|
Evaluation of hyperthyroidism is presented in Figure 863.1.
Figure 863.1 Evaluation of hyperthyroidism. TSH: thyroid stimulating hormone; FT4: free T4; FT3: free T3; TRAb: TSH receptor antibody; TRH: Thyrotropin releasing hormone
Hypothyroidism is a condition caused by deficiency of thyroid hormones. Causes of hypothyroidism are listed in Table 863.3. Primary hypothyroidism results from deficient thyroid hormone biosynthesis that is not due to disorders of hypothalamus or pituitary. Secondary hypothyroidism results from deficient secretion of TSH from pituitary. Deficient or loss of secretion of thyro-tropin releasing hormone from hypothalamus results in tertiary hypothyroidism. Secondary and tertiary hypothyroidism are much less common than primary. Plasma TSH is high in primary and low in secondary and tertiary hypothyroidism. Differences between primary and secondary hypothyroidism are shown in Table 863.4.
Table 863.3 Causes of hypothyroidism
Table 863.4 Differences between primary and secondary hypothyroidism
|Parameter||Primary hypothyroidism||Secondary hypothyroidism|
|1. Cause||Hashimoto’s thyroiditis||Pituitary disease|
|2. Serum TSH||High||Low|
|3. Thyrotropin releasing hormone stimulation test||Exaggerated response||No response|
|4. Antimicrosomal antibodies||Present||Absent|
Box 863.3 Thyroid function tests in hypothyroidism
Clinical features of primary hypothyroidism are: lethargy, mild depression, disturbances in menstruation, weight gain, cold intolerance, dry skin, myopathy, constipation, and firm and lobulated thyroid gland (in Hashimoto’s thyroiditis).
In severe cases, myxoedema coma (an advanced stage with stupor, hypoventilation, and hypothermia) can occur.
Laboratory features in hypothyroidism are shown in Box 863.3.
Normal serum thyroxine (T4 and FT4) coupled with a moderately raised TSH (>10 mU/L) is referred to as subclinical hypothyroidism. It is associated with bad obstetrical outcome, poor cognitive development in children, and high risk of hypercholesterolemia and progression to overt hypothyroidism.
Evaluation of hypothyroidism is presented in Figure 863.2
Figure 863.2 Evaluation of hypothyroidism. TSH: thyroid stimulating hormone; FT4: free T4; TRH: Thyrotropin releasing hormone
- 22 Sep 2017
The ovaries are the sites of production of female gametes or ova by the process of oogenesis. The ova are released by the process of ovulation in a cyclical manner at regular intervals. Ovary contains numerous follicles that contain ova in various stages of development. During each menstrual cycle, up to 20 primordial follicles are activated for maturation; however, only one follicle becomes fully mature; this dominant follicle ruptures to release the secondary oocyte from the ovary. Maturation of the follicle is stimulated by follicle stimulating hormone (FSH) secreted by anterior pituitary (Figure 862.1). Maturing follicle secretes estrogen that causes proliferation of endometrium of the uterus (proliferative phase). Follicular cells also secrete inhibin which regulates release of FSH by the anterior pituitary. Fall in FSH level is followed by secretion of luteinizing hormone (LH) by the anterior pituitary (LH surge). This causes follicle to rupture and the ovum is expelled into the peritoneal cavity near the fimbrial end of the fallopian tube. The fallopian tubes conduct ova from the ovaries to the uterus. Fertilization of ovum by the sperm occurs in the fallopian tube.
Figure 862.1 The hypothalamus-pituitary-ovarian axis
The ovum consists of the secondary oocyte, zona pellucida and corona radiata. The ruptured follicle in the ovary collapses and fills with blood clot (corpus luteum). LH converts granulose cells in the follicle to lutein cells which begin to secrete progesterone. Progesterone stimulates secretion from the endometrial glands (secretory phase) that were earlier under the influence of estrogen. Rising progesterone levels inhibit LH production from the anterior pituitary. Without LH, the corpus luteum regresses and becomes functionless corpus albicans. After regression of corpus luteum, production of estrogen and progesterone stops and endometrium collapses, causing onset of menstruation. If the ovum is fertilized and implanted in the uterine wall, human chorionic gonadotropin (hCG) is secreted by the developing placenta into the maternal circulation. Human chorionic gonadotropin maintains the corpus luteum for secetion of estrogen and progesterone till 12th week of pregnancy. After 12th week, corpus luteum regresses to corpus albicans and the function of synthesis of estrogen and progesterone is taken over by placenta till parturition.
The average duration of the normal menstrual cycle is 28 days. Ovulation occurs around 14th day of the cycle. The time interval between ovulation and menstruation is called as luteal phase and is fairly constant (14 days) (Figure 862.2).
Figure 862.2 Normal menstrual cycle
Causes of Female Infertility
Causes of female infertility are shown in Table 862.1.
Table 862.1 Causes of female infertility
1. Hypothalamic-pituitary dysfunction:
2. Ovarian dysfunction:
|3. Dysfunction in passages:|
|4. Dysfunction of sexual act: Dyspareunia|
Evaluation of female infertility is shown in Figure 862.3.
Figure 862.3 Evaluation of female infertility. FSH: Follicle stimulating hormone; LH: Luteinizing hormone; DHEA-S: Dihydroepiandrosterone; TSH: Thyroid stimulating hormone; ↑ : Increased; ↓ : Decreased
Tests for Ovulation
Most common cause of female infertility is anovulation.
- Regular cycles, mastalgia, and laparoscopic direct visualization of corpus luteum indicate ovulatory cycles. Anovulatory cycles are clinically characterized by amenorrhea, oligomenorrhea, or irregular menstruation. However, apparently regular cycles may be associated with anovulation.
- Endometrial biopsy: Endometrial biopsy is done during premenstrual period (21st-23rd day of the cycle). The secretory endometrium during the later half of the cycle is an evidence of ovulation.
- Ultrasonography (USG): Serial ultrasonography is done from 10th day of the cycle and the size of the dominant follicle is measured. Size >18 mm is indicative of imminent ovulation. Collapse of the follicle with presence of few ml of fluid in the pouch of Douglas is suggestive of ovulation. USG also is helpful for treatment (i.e. timing of coitus or of intrauterine insemination) and diagnosis of luteinized unruptured follicle (absence of collapse of dominant follicle). Transvaginal USG is more sensitive than abdominal USG.
- Basal body temperature (BBT): Patient takes her oral temperature at the same time every morning before arising. BBT falls by about 0.5°F at the time of ovulation. During the second (progestational) half of the cycle, temperature is slightly raised above the preovulatory level (rise of 0.5° to 1°F). This is due to the slight pyrogenic action of progesterone and is therefore presumptive evidence of functional corpus luteum.
- Cervical mucus study:
• Fern test: During estrogenic phase, a characteristic pattern of fern formation is seen when cervical mucus is spread on a glass slide (Figure 862.4). This ferning disappears after the 21st day of the cycle. If previously observed, its disappearance is presumptive evidence of corpus luteum activity.
• Spinnbarkeit test: Cervical mucus is elastic and withstands stretching upto a distance of over 10 cm. This phenomenon is called Spinnbarkeit or the thread test for the estrogen activity. During the secretory phase, viscosity of the cervical mucus increases and it gets fractured when stretched. This change in cervical mucus is evidence of ovulation.
- Vaginal cytology: Karyopyknotic index (KI) is high during estrogenic phase, while it becomes low in secretory phase. This refers to percentage of super-ficial squamous cells with pyknotic nuclei to all mature squamous cells in a lateral vaginal wall smear. Usually minimum of 300 cells are evaluated. The peak KI usually corresponds with time of ovulation and may reach upto 50 to 85.
- Estimation of progesterone in mid-luteal phase (day 21 or 7 days before expected menstruation): Progesterone level > 10 nmol/L is a reliable evidence of ovulation if cycles are regular (Figure 862.5). A mistimed sample is a common cause of abnormal result.
Figure 862.4 Ferning of cervical mucosa
Figure 862.5 Serum progesterone during normal menstrual cycle
Tests to Determine the Cause of Anovulation
- Measurement of LH, FSH, and estradiol during days 2 to 6: All values are low in hypogonadotropic hypogonadism (hypothalamic or pituitary failure).
- Measurement of TSH, prolactin, and testosterone if cycles are irregular or absent:
Increased TSH: Hypothyroidism
Increased prolactin: Pituitary adenoma
Increased testosterone: Polycystic ovarian disease (PCOD), congenital adrenal hyperplasia (To differentiate PCOD from congenital adrenal hyperplasia, ultrasound and estimation of dihydroepiandrosterone or DHEA are done).
- Transvaginal ultrasonography: This is done for detection of PCOD.
Investigations to Assess Tubal and Uterine Status
- Infectious disease: These tests include endometrial biopsy for tuberculosis and test for chlamydial IgG antibodies for tubal factor in infertility.
- Hysterosalpingography (HSG): HSG is a radiological contrast study for investigation of the shape of the uterine cavity and for blockage of fallopian tubes (Figure 862.6). A catheter is introduced into the cervical canal and a radiocontrast dye is injected into the uterine cavity. A real time X-ray imaging is carried out to observe the flow of the dye into the uterine cavity, tubes, and spillage into the uterine cavity.
- Hysterosalpingo-contrast sonography: A catheter is introduced into the cervical canal and an echocontrast fluid is introduced into the uterine cavity. Shape of the uterine cavity, filling of fallopian tubes, and spillage of contrast fluid are noted. In addition, ultrasound scan of the pelvis provides information about any fibroids or polycystic ovarian disease.
- Laparoscopy and dye hydrotubation test with hysteroscopy: In this test, a cannula is inserted into the cervix and methylene blue dye is introduced into the uterine cavity. If tubes are patent, spillage of the dye is observed from the ends of both tubes. This technique also allows visualization of pelvic organs, endometriosis, and pelvic adhesions. If required, endometriosis and tubal blockage can be treated during the procedure.
Possible pregnancy and active pelvic or vaginal infection are contraindications to tubal patency tests.
Figure 862.6 Hysterosalpingography
- 22 Sep 2017
The male reproductive system consists of testes (paired organs located in the scrotal sac that produce spermatozoa and secrete testosterone), a paired system of ducts comprising of epididymis, vasa deferentia, and ejaculatory ducts (collect, store, and conduct spermatozoa), paired seminal vesicles and a single prostate gland (produce nutritive and lubricating seminal fluid), bulbourethral glands of Cowper (secrete lubricating mucus), and penis (organ of copulation).
The hypothalamus secretes gonadotropin releasing hormone (GnRH) that regulates the secretion of the two gonadotropins from the anterior pituitary: luteinizing hormone (LH) and follicle stimulating hormone (FSH) (Figure 861.1). Luteinizing hormone primarily stimulates the production and secretion of testosterone from Leydig cells located in the interstitial tissue of the testes. Testosterone stimulates spermatogenesis, and plays a role in the development of secondary sexual characters. Testosterone needs to be converted to an important steroidal metabolite, dihydrotestosterone within cells to perform most of its androgenic functions. Testosterone inhibits LH secretion by negative feedback. Follicle stimulating hormone acts on Sertoli cells of seminiferous tubules to regulate the normal maturation of the sperms. Sertoli cells produce inhibin that controls FSH secretion by negative feedback.
Figure 861.1 Hypothalamus-pituitary-testis axis. + indicates stimulation; – indicates negative feedback
During sexual intercourse, semen is deposited into the vagina. Liquefaction of semen occurs within 20-30 minutes due to proteolytic enzymes of prostatic fluid. For fertilization to occur in vivo, the sperm must undergo capacitation and acrosome reaction. Capacitation refers to physiologic changes in sperms that occur during their passage through the cervix of the female genital tract. With capacitation, the sperm acquires (i) ability to undergo acrosome reaction, (ii) ability to bind to zona pellucida, and (iii) hypermotility. Sperm then travels through the cervix and uterus up to the fallopian tube. Binding of sperm to zona pellucida induces acrosomal reaction (breakdown of outer plasma membrane by enzymes of acrosome and its fusion with outer acrosomal membrane, i.e. loss of acrosome). This is necessary for fusion of sperm and oocyte membranes. Acrosomal reaction and binding of sperm and ovum surface proteins is followed by penetration of zona pellucida of ovum by the sperm. Following penetration by sperm, hardening of zona pellucida occurs that inhibits penetration by additional sperms. A sperm penetrates and fertilizes the egg in the ampullary portion of the fallopian tube (Figure 861.2).
Figure 861.2 Steps before and after fertilization of ovum
Causes of Male Infertility
Causes of male infertility are listed in Table 861.1.
Table 861.1 Causes of male infertility
2. Hypothalamic-pituitary dysfunction (hypogonadotropic hypogonadism)
3. Testicular dysfunction:
4. Dysfunction of passages and accessory sex glands:
5. Dysfunction of sexual act:
Investigations of Male Infertility
- History: This includes type of lifestyle (heavy smoking, alcoholism), sexual practice, erectile dysfunction, ejaculation, sexually transmitted diseases, surgery in genital area, drugs, and any systemic illness.
- Physical examination: Examination of reproductive system should includes testicular size, undescended testes, hypospadias, scrotal abnormalities (like varicocele), body hair, and facial hair. Varicocele can occur bilaterally and is the most common surgically removable abnormality causing male infertility.
- Semen analysis: See article Semen Analysis. Evaluation of azoospermia is shown in Figure 861.3. Evaluation of low semen volume is shown in Figure 861.4.
- Chromosomal analysis: This can reveal Klinefelter’s syndrome (e.g. XXY karyotype) (Figure 861.5), deletion in Y chromosome, and autosomal Robertsonian translocation. It is necessary to screen for cystic fibrosis carrier state if bilateral congenital absence of vas deferens is present.
- Hormonal studies: This includes measurement of FSH, LH, and testosterone to detect hormonal abnormalities causing testicular failure (Table 861.2).
- Testicular biopsy: Testicular biopsy is indicated when differentiation between obstructive and non-obstructive azoospermia is not evident (i.e. normal FSH and normal testicular volume).
Table 861.2 Interpretation of hormonal studies in male infertility
|Follicle stimulating hormone||Luteinizing hormone||Testosterone||Interpretation|
|Low||Low||Low||Hypogonadotropic hypogonadism (Hypothalamic or pituitary disorder)|
|High||High||Low||Hypergonadotropic hypogonadism (Testicular disorder)|
|Normal||Normal||Normal||Obstruction of passages, dysfunction of accessory glands|
Figure 861.3 Evaluation of azoospermia. FSH: Follicle stimulating hormone; LH: Luteinizing hormone
Figure 861.4 Evaluation of low semen volume
Figure 861.5 Karyotype in Klinefelter’s syndrome (47, XXY)
Common initial investigations for diagnosis of cause of infertility are listed below.
- 08 Sep 2017
Anatomically, stomach is divided into four parts: cardia, fundus, body, and pyloric part. Cardia is the upper part surrounding the entrance of the esophagus and is lined by the mucus-secreting epithelium. The epithelium of the fundus and the body of the stomach is composed of different cell types including: (i) mucus-secreting cells which protect gastric mucosa from self-digestion by forming an overlying thick layer of mucus, (ii) parietal cells which secrete hydrochloric acid and intrinsic factor, and (iii) peptic cells or chief cells which secrete the proteolytic enzyme pepsinogen. Pyloric part is divided into pyloric antrum and pyloric canal. It is lined by mucus-secreting cells and gastrin-secreting neuroendocrine cells (G cells) (Figure 859.1).
Figure 859.1 Parts of stomach and their lining cells
In the stomach, ingested food is mechanically and chemically broken down to form semi-digested liquid called chyme. Following relaxation of pyloric sphincter, chyme passes into the duodenum.
There are three phases of gastric acid secretion: cephalic, gastric, and intestinal.
- Cephalic or neurogenic phase: This phase is initiated by the sight, smell, taste, or thought of food that causes stimulation of vagal nuclei in the brain. Vagus nerve directly stimulates parietal cells to secrete acid; in addition, it also stimulates antral G cells to secrete gastrin in blood (which is also a potent stimulus for gastric acid secretion) (Figure 859.2). Cephalic phase is abolished by vagotomy.
- Gastric phase: Entry of swallowed food into the stomach causes gastric distension and induces gastric phase. Distension of antrum and increase in pH due to neutralization of acid by food stimulate antral G cells to secrete gastrin into the circulation. Gastrin, in turn, causes release of hydrochloric acid from parietal cells.
- Intestinal phase: Entry of digested proteins into the duodenum causes an increase in acid output from the stomach. It is thought that certain hormones and absorbed amino acids stimulate parietal cells to secrete acid.
The secretion from the stomach is called as gastric juice. The chief constituents of the gastric juice are:
- Hydrochloric acid (HCl): This is secreted by the parietal cells of the fundus and the body of the stomach. HCl provides the high acidic pH necessary for activation of pepsinogen to pepsin. Gastric acid secretion is stimulated by histamine, acetylcholine, and gastrin (Figure 859.2). HCl kills most microorganisms entering the stomach and also denatures proteins (breaks hydrogen bonds making polypeptide chains to unfold). Its secretion is inhibited by somatostatin (secreted by D cells in pancreas and by mucosa of intestine), gastric inhibitory peptide (secreted by K cells in duodenum and jejunum), prostaglandin, and secretin (secreted by S cells in duodenum).
- Pepsin: Pepsin is secreted by chief cells in stomach. Pepsin causes partial digestion of proteins leading to the formation of large polypeptide molecules (optimal function at pH 1.0 to 3.0). Its secretion is enhanced by vagal stimulation.
- Intrinsic factor (IF): IF is necessary for absorption of vitamin B12 in the terminal ileum. It is secreted by parietal cells of stomach.
Figure 859.2 Stimulation of gastric acid secretion. Three receptors on parietal cells stimulate acid secretion: histamine (H2) receptor, acetylcholine or cholinergic receptor, and gastrin/CCK-B receptor. Histamine is released by enterochromaffin-like cells in lamina propria. Acetylcholine is released from nerve endings. Gastrin is released from G cells in antrum (in response to amino acids in food, antral distention, and gastrin-releasing peptide). After binding to receptors, H+ is secreted in exchange for K+ by proton pump
- 07 Sep 2017
- Gastric intubation for gastric analysis is contraindicated in esophageal stricture or varices, active nasopharyngeal disease, diverticula, malignancy, recent history of severe gastric hemorrhage, hypertension, aortic aneurysm, cardiac arrhythmias, congestive cardiac failure, or non-cooperative patient.
- Pyloric stenosis: Obstruction of gastric outlet can elevate gastric acid output due to raised gastrin (following antral distension).
- Pentagastrin stimulation is contraindicated in cases with allergy to pentagastrin, and recent severe gastric hemorrhge due to peptic ulcer disease.
Gastric analysis is not a commonly performed procedure because of following reasons:
- It is an invasive and cumbersome technique that is traumatic and unpleasant for the patient.
- Information obtained is not diagnostic in itself.
- Availability of better tests for diagnosis such as endoscopy and radiology (for suspected peptic ulcer or malignancy); serum gastrin estimation (for ZE syndrome); vitamin assays, Schilling test, and antiparietal cell antibodies (for pernicious anemia); and tests for Helicobacter pylori infection (in duodenal or gastric ulcer).
- Availability of better medical line of treatment that obviates need for surgery in many patients.
- 07 Sep 2017
- Hollander’s test (Insulin hypoglycemia test): In the past, this test was used for confirmation of completeness of vagotomy (done for duodenal ulcer).
Hypoglycemia is a potent stimulus for gastric acid secretion and is mediated by vagus nerve. This response is abolished by vagotomy.
In this test, after determining BAO, insulin is administered intravenously (0.15-0.2 units/kg) and acid output is estimated every 15 minutes for 2 hours (8 post-stimulation samples). Vagotomy is considered as complete if, after insulin-induced hypoglycemia (blood glucose < 45 mg/dl), no acid output is observed within 45 minutres.
The test gives reliable results only if blood glucose level falls below 50 mg/dl at some time following insulin injection. It is best carried out after 3-6 months of vagotomy.
The test is no longer recommended because of the risk associated with hypoglycemia. Myocardial infarction, shock, and death have also been reported.
- Fractional test meal: In the past, test meals (e.g. oat meal gruel, alcohol) were administered orally to stimulate gastric secretion and determine MAO or PAO. Currently, parenteral pentagastrin is the gastric stimulant of choice.
- Tubeless gastric analysis: This is an indirect and rapid method for determining output of free hydrochloric acid in gastric juice. In this test, a cationexchange resin tagged to a dye (azure A) is orally administered. In the stomach, the dye is displaced from the resin by the free hydrogen ions of the hydrochloric acid. The displaced azure A is absorbed in the small intestine, enters the bloodstream, and is excreted in urine. Urinary concentration of the dye is measured photometrically or by visual comparison with known color standards. The quantity of the dye excreted is proportional to the gastric acid output. However, if kidney or liver function is impaired, false results may be obtained. The test is no longer in use.
- Spot check of gastric pH: According to some investigators, spot determination of pH of fasting gastric juice (obtained by nasogastric intubation) can detect the presence of hypochlorhydria (if pH>5.0 in men or >7.0 in women).
- Congo red test during esophagogastroduodenoscopy: This test is done to determine the completeness of vagotomy. Congo red dye is sprayed into the stomach during esophagogastroduodenoscopy; if it turns red, it indicates presence of functional parietal cells in stomach with capacity of producing acid.
- Volume of gastric juice: 20-100 ml
- Appearance: Clear
- pH: 1.5 to 3.5
- Basal acid output: Up to 5 mEq/hour
- Peak acid output: 1 to 20 mEq/hour
- Ratio of basal acid output to peak acid output: <0.20 or < 20%
- 07 Sep 2017
In gastric analysis, amount of acid secreted by the stomach is determined on aspirated gastric juice sample. Gastric acid output is estimated before and after stimulation of parietal cells (i.e. basal and peak acid output). This test was introduced in the past mainly for the evaluation of peptic ulcer disease (to assess the need for operative intervention). However, diminishing frequency of peptic ulcer disease and availability of safe and effective medical treatment have markedly reduced the role of surgery.
- To determine the cause of recurrent peptic ulcer disease:
• To detect Zollinger-Ellison (ZE) syndrome: ZE syndrome is a rare disorder in which multiple mucosal ulcers develop in the stomach, duodenum, and upper jejunum due to gross hypersecretion of acid in the stomach. The cause of excess secretion of acid is a gastrin-producing tumor of pancreas. Gastric analysis is done to detect markedly increased basal and pentagastrinstimulated gastric acid output for diagnosis of ZE syndrome (and also to determine response to acidsuppressant therapy). However, a more sensitive and specific test for diagnosis of ZE syndrome is measurement of serum gastrin (fasting and secretin-stimulated).
• To decide about completeness of vagotomy following surgery for peptic ulcer disease: See Hollander’s test.
- To determine the cause of raised fasting serum gastrin level: Hypergastrinemia can occur in achlorhydria, Zollinger-Ellison syndrome, and antral G cell hyperplasia.
- To support the diagnosis of pernicious anemia (PA): Pernicious anemia is caused by defective absorption of vitamin B12 due to failure of synthesis of intrinsic factor secondary to gastric mucosal atrophy. There is also absence of hydrochloric acid in the gastric juice (achlorhydria). Gastric analysis is done for demonstration of achlorhydria if facilities for vitamin assays and Schilling’s test are not available (Achlorhydria by itself is insufficient for diagnosis of PA).
- To distinguish between benign and malignant ulcer: Hypersecretion of acid is a feature of duodenal peptic ulcer, while failure of acid secretion (achlorhydria) occurs in gastric carcinoma. However, anacidity occurs only in a small proportion of cases with advanced gastric cancer. Also, not all patients with duodenal ulcer show increased acid output.
- To measure the amount of acid secreted in a patient with symptoms of peptic ulcer dyspepsia but normal X-ray findings: Excess acid secretion in such cases is indicative of duodenal ulcer. However, hypersecretion of acid does not always occur in duodenal ulcer.
- To decide the type of surgery to be performed in a patient with peptic ulcer: Raised basal as well as peak acid outputs indicate increased parietal cell mass and need for gastrectomy. Raised basal acid output with normal peak output is an indication for vagotomy.
- 05 Sep 2017
To assess gastric acid secretion, acid output from the stomach is measured in a fasting state and after injection of a drug which stimulates gastric acid secretion.
Basal acid output (BAO) is the amount of hydrochloric acid (HCl) secreted in the absence of any external stimuli (visual, olfactory, or auditory).
Maximum acid output (MAO) is the amount of hydrochloric acid secreted by the stomach following stimulation by pentagastrin. MAO is calculated from the first four 15-minute samples after stimulation.
Peak acid output (PAO) is calculated from the two highest consecutive 15-minute samples. It indicates greatest possible acid secretory capacity and is preferred over MAO as it is more reproducible.
Acidity is estimated by titration.
Collection of Sample
All drugs that affect gastric acid secretion (e.g. antacids, anticholinergics, cholinergics, H2-receptor antagonists, antihistamines, tranquilizers, antidepressants, and carbonic anhydrase inhibitors) should be withheld for 24 hours before the test. Proton pump inhibitors should be discontinued 5 days prior to the test. Patient should be relaxed and free from all sources of sensory stimulation.
Patient should drink or eat nothing after midnight.
Gastric juice can be aspirated through an oral or nasogastric tube (polyvinyl chloride, silicone, or polyurethane) or during endoscopy.
Oral or nasogastric tube (Figure 855.1) is commonly used. It is a flexible tube having a small diameter and a bulbous end that is made heavy by a small weight of lead. The end is perforated with small holes to allow entry of gastric juice into the tube. As the end is radiopaque, the tube can be positioned in the most dependent part of the stomach under fluoroscopic or X-ray guidance. The tube is lubricated and can be introduced either through the mouth or the nose. The patient is either sitting or reclining on left side. The tube has three or four markings on its outer surface that correspond with distance of the tip of the tube from the teeth, i.e. 40 cm (tip to cardioesophageal junction), 50 cm (body of stomach), 57 cm (pyloric antrum), and 65 cm (duodenum). The position of the tube can be verified either by fluoroscope or by ‘water recovery test’. In the latter test, 50 ml of water is introduced through the tube and aspirated again; recovery of > 90% of water is indicative of proper placement. The tube is usually positioned in the antrum. A syringe is attached to the outer end of the tube for the aspiration of gastric juice.
Figure 855.1 Oral or nasogastric Ryle’s tube. The tube is marked at 40, 50, 57, and 65 cm with radiopaque lines for accurate placement. The tip is bulbous and contains a small weight of lead to assist the passage during intubation and to know the position under fluoroscopy or X-ray guidance. There are four perforations or eyes to aspirate contents from the stomach through a syringe attached to the base
For estimation of BAO, sample is collected in the morning after 12-hour overnight fast. Gastric secretion that has accumulated overnight is aspirated and discarded. This is followed by aspiration of gastric secretions at 15-minute intervals for 1 hour (i.e. total 4 consecutive samples are collected). All the samples are centrifuged to remove any particulate matter. Each 15-minute sample is analyzed for volume, pH, and acidity. The acid output in the four samples is totaled and the result is expressed as concentration of acid in milliequivalents per hour or in mmol per hour.
After the collection of gastric juice for determination of BAO, patient is given a subcutaneous or intramuscular injection of pentagastrin (6 μg/kg of body weight), and immediately afterwards, gastric secretions are aspirated at 15-minute intervals for 1 hour (for estimation of MAO or PAO). MAO is calculated from the first four 15-minute samples after stimulation. PAO is calculated from two consecutive 15-minute samples showing highest acidity.
Box 855.1 Determination of basal acid output, maximum acid output, and peak acid output
Gastric acidity is estimated by titration, with the end point being determined either by noting the change in color of the indicator solution or till the desired pH is reached.
In titration, a solution of alkali (0.1 N sodium hydroxide) is added from a graduated vessel (burette) to a known volume of acid (i.e. gastric juice) till the end point or equivalence point of reaction is reached. The concentration of acid is then determined from the concentration and volume of alkali required to neutralize the particular volume of gastric juice. Concentration of acid is expressed in terms of milliequivalents per liter or mmol per liter.
Free acidity refers to the concentration of HCl present in a free, uncombined form in a solution. The volume of alkali added to the gastric juice till the Topfer’s reagent (an indicator added earlier to the gastric juice) changes color or when the pH (as measured by the pH meter) reaches 3.5 is a measure of free acidity. A screening test can be carried out for the presence of free HCl in the gastric juice. If red color develops after addition of a drop of Topfer’s reagent to an aliquot of gastric juice, free HCl is present and the diagnosis of pernicious anaemia (achlorhydria) can be excluded.
Combined acidity refers to the amount of HCl combined with proteins and mucin and also includes small amount of weak acids present in gastric juice.
Total acidity is the sum of free and combined acidity. The amount of alkali added to the gastric juice till phenolphthalein indicator (added earlier to the gastric juice) changes color is a measure of total acidity (Box 855.1).
Interpretation of Results
- Volume: Normal total volume is 20-100 ml (usually < 50 ml). Causes of increased volume of gastric juice are—
• Delayed emptying of stomach: pyloric stenosis
• Increased gastric secretion: duodenal ulcer, Zollinger-Ellison syndrome.
- Color: Normal gastric secretion is colorless, with a faintly pungent odor. Fresh blood (due to trauma, or recent bleeding from ulcer or cancer) is red in color. Old hemorrhage produces a brown, coffee-ground like appearance (due to formation of acid hematin). Bile regurgitation produces a yellow or green color.
- pH: Normal pH is 1.5 to 3.5. In pernicious anemia, pH is greater than 7.0 due to absence of HCl.
- Basal acid output:
• Normal: Up to 5 mEq/hour.
• Duodenal ulcer: 5-15 mEq/hour.
• Zollinger-Ellison syndrome: >20 mEq/hour.
Normal BAO is seen in gastric ulcer and in some patients with duodenal ulcer.
- Peak acid output:
• Normal: 1-20 mEq/hour.
• Duodenal ulcer: 20-60 mEq/hour.
• Zollinger-Ellison syndrome: > 60 mEq/hour.
• Achlorhydria: 0 mEq/hour.
Normal PAO is seen in gastric ulcer and gastric carcinoma. Values up to 60 mEq/hour can occur in some normal individuals and in some patients with Zollinger-Ellison syndrome.
In pernicious anemia, there is no acid output due to gastric mucosal atrophy. Achlorhydria should be diagnosed only if there is no free HCl even after maximum stimulation.
- Ratio of basal acid output to peak acid output (BAO/PAO):
• Normal: < 0.20 (or < 20%).
• Gastric or duodenal ulcer: 0.20-0.40 (20-40%).
• Duodenal ulcer: 0.40-0.60 (40-60%).
• Zollinger-Ellison syndrome: > 0.60 (> 60%).
Normal values occur in gastric ulcer or gastric carcinoma.
Conditions associated with change in gastric acid output are listed in Table 855.1.
It is to be noted that values of acid output are not diagnostic by themselves and should be correlated with clinical, radiological, and endoscopic features.
Table 855.1 Causes of alterations in gastric acid output
|Increased gastric acid output||Decreased gastric acid output|
|• Duodenal ulcer||• Chronic atrophic gastritis|
|• Zollinger-Ellison syndrome||1. Pernicious anemia|
|• Hyperplasia of antral G cells||2. Rheumatoid arthritis|
|• Systemic mastocytosis||3. Thyrotoxicosis|
|• Basophilic leukemia||• Gastric ulcer|
|• Gastric carcinoma|
|• Chronic renal failure|
- 04 Sep 2017
Bioethics is the study of the ethical issues emerging from advances in biology and medicine. It is also moral discernment as it relates to medical policy and practice. Bioethicists are concerned with the ethical questions that arise in the relationships among life sciences, biotechnology, medicine, politics, law, and philosophy. It includes the study of values ("the ethics of the ordinary") relating to primary care and other branches of medicine.
- 04 Sep 2017
Animal biotechnology is a branch of biotechnology in which molecular biology techniques are used to genetically engineer (i.e. modify the genome of) animals in order to improve their suitability for pharmaceutical, agricultural or industrial applications. Animal biotechnology has been used to produce genetically modified animals that synthesize therapeutic proteins, have improved growth rates or are resistant to disease.
- 04 Sep 2017
Biophysics or biological physics is an interdisciplinary science that applies the approaches and methods of physics to study biological systems. Biophysics covers all scales of biological organization, from molecular to organismic and populations. Biophysical research shares significant overlap with biochemistry, physical chemistry, nanotechnology, bioengineering, computational biology, biomechanics and systems biology.
- 04 Sep 2017
Histopathology (compound of three Greek words: ἱστός histos "tissue", πάθος pathos "suffering", and -λογία -logia"study of") refers to the microscopic examination of tissue in order to study the manifestations of disease. Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides. In contrast, cytopathology examines (1) free cells or (2) tissue micro-fragments (as "cell blocks").
- 04 Sep 2017
Physiology (/ˌfɪziˈɒlədʒi/; from Ancient Greek φύσις (physis), meaning 'nature, origin', and -λογία (-logia), meaning 'study of') is the scientific study of normal mechanisms, and their interactions, which works within a living system. A sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system. Given the size of the field, it is divided into, among others, animal physiology (including that of humans), plant physiology, cellular physiology, microbial physiology (microbial metabolism), bacterial physiology, and viral physiology.
Central to an understanding of physiological functioning is its integrated nature with other disciplines such as chemistry and physics, coordinated homeostatic control mechanisms, and continuous communication between cells.
The Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences. In medicine, a physiologic state is one occurring from normal body function, rather than pathologically, which is centered on the abnormalities that occur in animal diseases, including humans.
- 04 Sep 2017
Food science is the applied science devoted to the study of food. The Institute of Food Technologists defines food science as "the discipline in which the engineering, biological, and physical sciences are used to study the nature of foods, the causes of deterioration, the principles underlying food processing, and the improvement of foods for the consuming public". The textbook Food Science defines food science in simpler terms as "the application of basic sciences and engineering to study the physical, chemical, and biochemical nature of foods and the principles of food processing".
- 04 Sep 2017
Ecology (from Greek: οἶκος, "house", or "environment"; -λογία, "study of") is the scientific analysis and study of interactions among organisms and their environment. It is an interdisciplinary field that includes biology, geography, and Earth science. Ecology includes the study of interactions that organisms have with each other, other organisms, and with abiotic components of their environment. Topics of interest to ecologists include the diversity, distribution, amount (biomass), and number (population) of particular organisms, as well as cooperation and competition between organisms, both within and among ecosystems. Ecosystems are composed of dynamically interacting parts including organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and various niche construction activities, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits, and the variety of organisms is called biodiversity. Biodiversity, which refers to the varieties of species, genes, and ecosystems, enhances certain ecosystem services.
Ecology is not synonymous with environment, environmentalism, natural history, or environmental science. It is closely related to evolutionary biology, genetics, and ethology. An important focus for ecologists is to improve the understanding of how biodiversity affects ecological function. Ecologists seek to explain:
- Life processes, interactions, and adaptations
- The movement of materials and energy through living communities
- The successional development of ecosystems
- The abundance and distribution of organisms and biodiversity in the context of the environment.
There are many practical applications of ecology in conservation biology, wetland management, natural resource management(agroecology, agriculture, forestry, agroforestry, fisheries), city planning (urban ecology), community health, economics, basic and applied science, and human social interaction (human ecology). For example, the Circles of Sustainability approach treats ecology as more than the environment 'out there'. It is not treated as separate from humans. Organisms (including humans) and resources compose ecosystems which, in turn, maintain biophysical feedback mechanisms that moderate processes acting on living (biotic) and non-living (abiotic) components of the planet. Ecosystems sustain life-supporting functions and produce natural capital like biomass production (food, fuel, fiber, and medicine), the regulation of climate, global biogeochemical cycles, water filtration, soil formation, erosion control, flood protection, and many other natural features of scientific, historical, economic, or intrinsic value.
The word "ecology" ("Ökologie") was coined in 1866 by the German scientist Ernst Haeckel (1834–1919). Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics. Ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology became a much more rigorous science in the late 19th century. Evolutionary concepts relating to adaptation and natural selection became the cornerstones of modern ecological theory.
- 04 Sep 2017
Forensic science is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal procedure.
Forensic scientists collect, preserve, and analyze scientific evidence during the course of an investigation. While some forensic scientists travel to the scene of the crime to collect the evidence themselves, others occupy a laboratory role, performing analysis on objects brought to them by other individuals.
In addition to their laboratory role, forensic scientists testify as expert witnesses in both criminal and civil cases and can work for either the prosecution or the defense. While any field could technically be forensic, certain sections have developed over time to encompass the majority of forensically related cases.
- 30 Aug 2017
Microscopic examinations done on fecal sample are shown in Figure 846.1.
Figure 846.1 Microscopic examinations carried out on fecal sample
Collection of Specimen for Parasites
A random specimen of stool (at least 4 ml or 4 cm³) is collected in a clean, dry, container with a tightly fitting lid (a tin box, plastic box, glass jar, or waxed cardboard box) and transported immediately to the laboratory (this is because trophozoites of Entameba histolytica rapidly degenerate and alter in morphology). About 20-40 grams of formed stool or 5-6 tablespoons of watery stool should be collected. Stool should not be contaminated with urine, water, soil, or menstrual blood. Urine and water destroy trophozoites; soil will introduce extraneous organisms and also hinder proper examination. Parasites are best detected in warm, freshly passed stools and therefore stools should be examined as early as possible after receipt in the laboratory (preferably within 1 hour of collection). If delay in examination is anticipated, sample may be refrigerated. A fixative containing 10% formalin (for preservation of eggs, larvae, and cysts) or polyvinyl alcohol (for preservation of trophozoites and cysts, and for permanent staining) may be used if specimen is to be transported to a distant laboratory.
One negative report for ova and parasites does not exclude the possibility of infection. Three separate samples, collected at 3-day intervals, have been recommended to detect all parasite infections.
Patient should not be receiving oily laxatives, antidiarrheal medications, bismuth, antibiotics like tetracycline, or antacids for 7 days before stool examination. Patient should not have undergone a barium swallow examination.
In the laboratory, macroscopic examination is done for consistency (watery, loose, soft or formed) (Figure 846.2), color, odor, and presence of blood, mucus, adult worms or segments of tapeworms.
Figure 846.2 Consistency of feces
Trophozoites are most likely to be found in loose or watery stools or in stools containing blood and mucus, while cysts are likely to be found in formed stools. Trophozoites die soon after being passed and therefore such stools should be examined within 1 hour of passing. Examination of formed stools can be delayed but should be completed on the same day.
Color/Appearance of Fecal Specimens
- Brown: Normal
- Black: Bleeding in upper gastrointestinal tract (proximal to cecum), Drugs (iron salts, bismuth salts, charcoal)
- Red: Bleeeding in large intestine, undigested tomatoes or beets
- Clay-colored (gray-white): Biliary obstruction
- Silvery: Carcinoma of ampulla of Vater
- Watery: Certain strains of Escherichia coli, Rotavirus enteritis, cryptosporidiosis
- Rice water: Cholera
- Unformed with blood and mucus: Amebiasis, inflammatory bowel disease
- Unformed with blood, mucus, and pus: Bacillary dysentery
- Unformed, frothy, foul smelling, which float on water: Steatorrhea.
Preparation of Slides
After receipt in the laboratory, saline and iodine wet mounts of the sample are prepared (Figure 846.3).
Figure 846.3 Saline and iodine wet mounts of fecal sample
A drop of normal saline is placed near one end of a glass slide and a drop of Lugol iodine solution is placed near the other end. A small amount of feces (about the size of a match-head) is mixed with a drop each of saline and iodine using a wire loop, and a cover slip is placed over each preparation separately. If the specimen contains blood or mucus, that portion should be included for examination (trophozoites are more readily found in mucus). If the stools are liquid, select the portion from the surface for examination.
Saline wet mount is used for demonstration of eggs and larvae of helminths, and trophozoites and cysts of protozoa. It can also detect red cells and white cells. Iodine stains glycogen and nuclei of the cysts. The iodine wet mount is useful for identification of protozoal cysts. Trophozoites become non-motile in iodine mounts. A liquid, diarrheal stool can be examined directly without adding saline.
Concentration of fecal specimen is useful if very small numbers of parasites are present. However, in concentrated specimens, amebic trophozoites can no longer be detected since they are destroyed. If wet mount examination is negative and there is clinical suspicion of parasitic infection, fecal concentration is indicated. It is used for detection of ova, cysts, and larvae of parasites.
Various concentration methods are available; the choice depends on the nature of parasites to be identified and the equipment/reagent available in a particular laboratory. Concentration techniques are of two main types:
- Sedimentation techniques: Ova and cysts settle at the bottom. However, excessive fecal debris may make the detection of parasites difficult. Example: Formolethyl acetate sedimentation procedure.
- Floatation techniques: Ova and cysts float on surface. However, some ova and cysts do not float at the top in this procedure. Examples: Saturated salt floatation technique and zinc sulphate concentration technique.
The most commonly used sedimentation method is formol-ethyl acetate concentration method since: (i) it can detect eggs and larvae of almost all helminths, and cysts of protozoa, (ii) it preserves their morphology well, (iii) it is rapid, and (iv) risk of infection to the laboratory worker is minimal because pathogens are killed by formalin.
In this method, fecal suspension is prepared in 10% formalin (10 ml formalin + 1 gram feces). This suspension is then passed through a gauze filter till 7 ml of filtered material is obtained. To this, ethyl acetate (3 ml) is added and the mixture is centrifuged for 1 minute. Eggs, larvae, and cysts sediment at the bottom of the centrifuge tube (Figure 846.4). Above this deposit, there are layers of formalin, fecal debris, and ether. Fecal debris is loosened with an applicator stick and the supernatant is poured off. One drop of sediment is placed on one end of a glass slide and one drop is placed at the other end. One of the drops is stained with iodine, cover slips are placed, and the preparation is examined under the microscope.
Figure 846.4 Formol-ethyl acetate concentration technique
Classification of Intestinal Parasites of Humans
Intestinal parasites of humans are classified into two main kingdoms: protozoa and metazoa (helminths) (Figure 846.5).
Figure 846.5 Classification of intestinal parasites of humans
- 30 Aug 2017
Chemical examination of feces is usually carried out for the following tests (Figure 845.1):
- Occult blood
- Excess fat excretion (malabsorption)
- Reducing sugars
- Fecal osmotic gap
- Fecal pH
Figure 845.1 Chemical examinations done on fecal sample
Test for Occult Blood in Stools
Presence of blood in feces which is not apparent on gross inspection and which can be detected only by chemical tests is called as occult blood. Causes of occult blood in stools are:
- Intestinal diseases: hookworms, amebiasis, typhoid fever, ulcerative colitis, intussusception, adenoma, cancer of colon or rectum.
- Gastric and esophageal diseases: peptic ulcer, gastritis, esophageal varices, hiatus hernia.
- Systemic disorders: bleeding diathesis, uremia.
- Long distance runners.
Occult blood test is recommended as a screening procedure for detection of asymptomatic colorectal cancer. Yearly examinations should be carried out after the age of 50 years. If the test is positive, endoscopy and barium enema are indicated.
Tests for detection of occult blood in feces: Many tests are available which differ in their specificity and sensitivity. These tests include tests based on peroxidase-like activity of hemoglobin (benzidine, orthotolidine, aminophenazone, guaiac), immunochemical tests, and radioisotope tests.
Tests Based on Peroxidase-like Activity of Hemoglobin
Principle: Hemoglobin has peroxidase-like activity and releases oxygen from hydrogen peroxide. Oxygen molecule then oxidizes the chemical reagent (benzidine, orthotolidine, aminophenazone, or guaiac) to produce a colored reaction product.
Benzidine and orthotolidine are carcinogenic and are no longer used. Benzidine test is also highly sensitive and false-positive reactions are common. Since bleeding from the lesion may be intermittent, repeated testing may be required.
Causes of False-positive Tests
- Ingestion of peroxidase-containing foods like red meat, fish, poultry, turnips, horseradish, cauliflower, spinach, or cucumber. Diet should be free from peroxidase-containing foods for at least 3 days prior to testing.
- Drugs like aspirin and other anti-inflammatory drugs, which increase blood loss from gastrointestinal tract in normal persons.
Causes of False-negative Tests
- Foods containing large amounts of vitamin C.
- Conversion of all hemoglobin to acid hematin (which has no peroxidase-like activity) during passage through the gastrointestinal tract.
These tests specifically detect human hemoglobin. Therefore there is no interference from animal hemoglobin or myoglobin (e.g. meat) or peroxidase-containing vegetables in the diet.
The test consists of mixing the sample with latex particles coated with anti-human haemoglobin antibody, and if agglutination occurs, test is positive. This test can detect 0.6 ml of blood per 100 grams of feces.
Radioisotope Test Using 51Cr
In this test, 10 ml of patient’s blood is withdrawn, labeled with 51Cr, and re-infused intravenously. Radioactivity is measured in fecal sample and in simultaneously collected blood specimen. Radioactivity in feces indicates gastrointestinal bleeding. Amount of blood loss can be calculated. Although the test is sensitive, it is not suitable for routine screening.
Apt test: This test is done to decide whether blood in the vomitus or in the feces of a neonate represents swallowed maternal blood or is the result of bleeding in the gastrointestinal tract. The test was devised by Dr. Apt and hence the name. The baby swallows blood during delivery or during breastfeeding if nipples are cracked. Apt test is based on the principle that if blood is of neonatal origin it will contain high proportion of hemoglobin F (Hb F) that is resistant to alkali denaturation. On the other hand, maternal blood mostly contains adult hemoglobin or Hb A that is less resistant.
Test for Malabsorption of Fat
Dietary fat is absorbed in the small intestine with the help of bile salts and pancreatic lipase. Fecal fat mainly consists of neutral fats (unsplit fats), fatty acids, and soaps (fatty acid salts). Normally very little fat is excreted in feces (<7 grams/day in adults). Excess excretion of fecal fat indicates malabsorption and is known as steatorrhea. It manifests as bulky, frothy, and foul-smelling stools, which float on the surface of water.
Causes of Malabsorption of Fat
- Deficiency of pancreatic lipase (insufficient lipolysis): chronic pancreatitis, cystic fibrosis.
- Deficiency of bile salts (insufficient emulsification of fat): biliary obstruction, severe liver disease, bile salt deconjugation due to bacterial overgrowth in the small intestine.
- Diseases of small intestine: tropical sprue, celiac disease, Whipple’s disease.
Tests for fecal fat are qualitative (i.e. direct microscopic examination after fat staining), and quantitative (i.e. estimation of fat by gravimetric or titrimetric analysis).
- Microscopic stool examination after staining for fat: A random specimen of stool is collected after putting the patient on a diet of >80 gm fat per day. Stool sample is stained with a fat stain (oil red O, Sudan III, or Sudan IV) and observed under the microscope for fat globules (Figure 845.2). Presence of ≥60 fat droplets/HPF indicates steatorrhea. Ingestion of mineral or castor oil and use of rectal suppositories can cause problems in interpretation.
- Quantitative estimation of fecal fat: The definitive test for diagnosis of fat malabsorption is quantitation of fecal fat. Patient should be on a diet of 70-100 gm of fat per day for 6 days before the test. Feces are collected over 72 hours and stored in a refrigerator during the collection period. Specimen should not be contaminated with urine. Fat quantitation can be done by gravimetric or titrimetric method. In gravimetric method, an accurately weighed sample of feces is emulsified, acidified, and fat is extracted in a solvent; after evaporation of solvent, fat is weighed as a pure compound. Titrimetric analysis is the most widely used method. An accurately weighed stool sample is treated with alcoholic potassium hydroxide to convert fat into soaps. Soaps are then converted to fatty acids by the addition of hydrochloric acid. Fatty acids are extracted in a solvent and the solvent is evaporated. The solution of fat made in neutral alcohol is then titrated against sodium hydroxide. Fatty acids comprise about 80% of fecal fat. Values >7 grams/day are usually abnormal. Values >14 grams/day are specific for diseases causing fat malabsorption.
Figure 845.2 Sudan stain on fecal sample: (A) Negative; (B) Positive
Test for Urobilinogen in Feces
Fecal urobilinogen is determined by Ehrlich’s aldehyde test (see Article “Test for Detection of Urobilinogen in Urine”). Specimen should be fresh and kept protected from light. Normal amount of urobilinogen excreted in feces is 50-300 mg per day. Increased fecal excretion of urobilinogen is seen in hemolytic anemia. Urobilinogen is deceased in biliary tract obstruction, severe liver disease, oral antibiotic therapy (disturbance of intestinal bacterial flora), and aplastic anemia (low hemoglobin turnover). Stools become pale or clay-colored if urobilinogen is reduced or absent.
Test for Reducing Sugars
Deficiency of intestinal enzyme lactase is a common cause of malabsorption. Lactase converts lactose (in milk) to glucose and galactose. If lactase is deficient, lactose is converted to lactic acid with production of gas. In infants this leads to diarrhea, vomiting, and failure to thrive. Benedict’s test or Clinitest™ tablet test for reducing sugars is used to test freshly collected stool sample for lactose. In addition, oral lactose tolerance test is abnormal (after oral lactose, blood glucose fails to rise above 20 mg/dl of basal value) in lactase deficiency. Rise in blood glucose indicates that lactose has been hydrolysed and absorbed by the mucosa. Lactose tolerance test is now replaced by lactose breath hydrogen testing. In lactase deficiency, accumulated lactose in the colon is rapidly fermented to organic acids and gases like hydrogen. Hydrogen is absorbed and then excreted through the lungs into the breath. Amount of hydrogen is then measured in breath; breath hydrogen more than 20 ppm above baseline within 4 hours indicates positive test.
Fecal Osmotic Gap
Fecal osmotic gap is calculated from concentration of electrolytes in stool water by formula 290-2([Na+] + [K+]). (290 is the assumed plasma osmolality). In osmotic diarrheas, osmotic gap is >150 mOsm/kg, while in secretory diarrhea, it is typically below 50 mOsm/kg. Evaluation of chronic diarrhea is shown in Figure 845.3.
Figure 845.3 Evaluation of chronic diarrhea
Stool pH below 5.6 is characteristic of carbohydrate malabsorption.
- 28 Aug 2017
Tests to Assess Proximal Tubular Function
Renal tubules efficiently reabsorb 99% of the glomerular filtrate to conserve the essential substances like glucose, amino acids, and water.
1. Glycosuria: In renal glycosuria, glucose is excreted in urine, while blood glucose level is normal. This is because of a specific tubular lesion which leads to impairment of glucose reabsorption. Renal glycosuria is a benign condition. Glycosuria can also occur in Fanconi syndrome.
2. Generalized aminoaciduria: In proximal renal tubular dysfunction, many amino acids are excreted in urine due to defective tubular reabsorption.
3. Tubular proteinuria (Low molecular weight proteinuria): Normally, low molecular weight proteins (β2 –microglobulin, retinol-binding protein, lysozyme, and α1 –microglobulin) are freely filtered by glomeruli and are completely reabsorbed by proximal renal tubules. With tubular damage, these low molecular weight proteins are excreted in urine and can be detected by urine protein electrophoresis. Increased amounts of these proteins in urine are indicative of renal tubular damage.
4. Urinary concentration of sodium: If both BUN and serum creatinine are acutely increased, it is necessary to distinguish between prerenal azotemia (renal underperfusion) and acute tubular necrosis. In prerenal azotemia, renal tubules are functioning normally and reabsorb sodium, while in acute tubular necrosis, tubular function is impaired and sodium absorption is decreased. Therefore, in prerenal azotemia, urinay sodium concentration is < 20 mEq/L while in acute tubular necrosis, it is > 20 mEq/L.
5. Fractional excretion of sodium (FENa): Measurement of urinary sodium concentration is affected by urine volume and can produce misleading results. Therefore, to avoid this, fractional excretion of sodium is calculated. This refers to the percentage of filtered sodium that has been absorbed and percentage that has been excreted. Measurement of fractional sodium excretion is a better indicator of tubular absorption of sodium than quantitation of urine sodium alone.
This test is indicated in acute renal failure. In oliguric patients, this is the most reliable means of early distinction between pre-renal failure and renal failure due to acute tubular necrosis. It is calculated from the following formula:
(Urine sodium × Plasma creatinine) × 100%
(Plasma sodium × Urine creatinine)
(Plasma sodium × Urine creatinine)
In pre-renal failure this ratio is less than 1%, and in acute tubular necrosis it is more than 1%. In pre-renal failure (due to reduced renal perfusion), aldosterone secretion is stimulated which causes maximal sodium conservation by the tubules and the ratio is less than 1%. In acute tubular necrosis, maximum sodium reabsorption is not possible due to tubular cell injury and consequently the ratio will be more than 1%. Values above 3% are strongly suggestive of acute tubular necrosis.
Tests to Assess Distal Tubular Function
1. Urine specific gravity: Normal specific gravity is 1.003 to 1.030. It depends on state of hydration and fluid intake.
- Causes of increased specific gravity:
a. Reduced renal perfusion (with preservation of concentrating ability of tubules),
e. Urinary tract obstruction.
- Causes of reduced specific gravity:
a. Diabetes insipidus
b. Chronic renal failure
c. Impaired concentrating ability due to diseases of tubules.
As a test of renal function, it gives information about the ability of renal tubules to concentrate the glomerular filtrate. This concentrating ability is lost in diseases of renal tubules.
Fixed specific gravity of 1.010, which cannot be lowered or increased by increasing or decreasing the fluid intake respectively, is an indication of chronic renal failure.
2. Urine osmolality: The most commonly employed test to evaluate tubular function is measurement of urine/plasma osmolality. This is the most sensitive method for determination of ability of concentration. Osmolality measures number of dissolved particles in a solution. Specific gravity, on the other hand, is the ratio of mass of a solution to the mass of water i.e. it measures total mass of solute. Specific gravity depends on both the number and the nature of dissolved particles while osmolality is exact number of solute particles in a solution. Specific gravity measurement can be affected by the presence of solutes of large molecular weight like proteins and glucose, while osmolality is not. Therefore measurement of osmolality is preferred.
When solutes are dissolved in a solvent, certain changes take place like lowering of freezing point, increase in boiling point, decrease in vapor pressure, or increase of osmotic pressure of the solvent. These properties are made use of in measuring osmolality by an instrument called as osmometer.
Osmolality is expressed as milliOsmol/kg of water.
Urine/plasma osmolality ratio is helpful in distinguishing pre-renal azotemia (in which ratio is higher) from acute renal failure due to acute tubular necrosis (in which ratio is lower). If urine and plasma osmolality are almost similar, then there is defective tubular reabsorption of water.
3. Water deprivation test: If the value of baseline osmolality of urine is inconclusive, then water deprivation test is performed. In this test, water intake is restricted for a specified period of time followed by measurement of specific gravity or osmolality. Normally, urine osmolality should rise in response to water deprivation. If it fails to rise, then desmopressin is administered to differentiate between central diabetes insipidus and nephrogenic diabetes insipidus. Urinary concentration ability is corrected after administration of desmopressin in central diabetes insipidus, but not in nephrogenic diabetes insipidus.
If urine osmolality is > 800 mOsm/kg of water or specific gravity is ≥1.025 following dehydration, concentrating ability of renal tubules is normal. However, normal result does not rule out presence of renal disease.
False result will be obtained if the patient is on low-salt, low-protein diet or is suffering from major electrolyte and water disturbance.
4. Water loading antidiuretic hormone suppression test: This test assesses the capacity of the kidney to make urine dilute after water loading.
After overnight fast, patient empties the bladder and drinks 20 ml/kg of water in 15-30 minutes. The urine is collected at hourly intervals for the next 4 hours for measurements of urine volume, specific gravity, and osmolality. Plasma levels of antidiuretic hormone and serum osmolality should be measured at hourly intervals.
Normally, more than 90% of water should be excreted in 4 hours. The specific gravity should fall to 1.003 and osmolality should fall to < 100 mOsm/kg. Plasma level of antidiuretic hormone should be appropriate for serum osmolality. In renal function impairment, urine volume is reduced (<80% of fluid intake is excreted) and specific gravity and osmolality fail to decrease. The test is also impaired in adrenocortical insufficiency, malabsorption, obesity, ascites, congestive heart failure, cirrhosis, and dehydration.
This test is not advisable in patients with cardiac failure or kidney disease. If there is failure to excrete water load, fatal hyponatremia can occur.
5. Ammonium chloride loading test (Acid load test): Diagnosis of renal tubular acidosis is usually considered after excluding other causes of metabolic acidosis. This test is considered as a ‘gold standard’ for the diagnosis of distal or type 1 renal tubular acidosis. Urine pH and plasma bicarbonate are measured after overnight fasting. If pH is less than 5.4, acidifying ability of renal tubules is normal. If pH is greater than 5.4 and plasma bicarbonate is low, diagnosis of renal tubular acidosis is confirmed. In both the above cases, further testing need not be performed. In all other cases in which neither of above results is obtained, further testing is carried out. Patient is given ammonium chloride orally (0.1 gm/kg) over 1 hour after overnight fast and urine samples are collected hourly for next 6-8 hours. Ammonium ion dissociates into H+ and NH3. Ammonium chloride makes blood acidic. If pH is less than 5.4 in any one of the samples, acidifying ability of the distal tubules is normal.
- 27 Aug 2017
Normally, a very small amount of albumin is excreted in urine. The earliest evidence of glomerular damage in diabetes mellitus is occurrence of microalbuminuria (albuminuria in the range of 30 to 300 mg/24 hours). An albuminuria > 300-mg/24 hour is termed clinical or overt and indicates significant glomerular damage. (See “Proteinuria” under Article “Chemical Examination of Urine”).
- 27 Aug 2017
Two biochemical parameters are commonly used to assess renal function: blood urea nitrogen (BUN) and serum creatinine. Although convenient, they are insensitive markers of glomerular function.
Blood Urea Nitrogen (BUN)
Urea is produced in the liver from amino acids (ingested or tissue-derived). Amino acids are utilized to produce energy, synthesize proteins, and are catabolized to ammonia. Urea is produced in the liver from ammonia in the Krebs urea cycle. Ammonia is toxic and hence is converted to urea, which is then excreted in urine (Figure 842.1).
Figure 842.1 Formation of urea from protein breakdown
The concentration of blood urea is usually expressed as blood urea nitrogen. This is because older methods estimated only the nitrogen in urea. Molecular weight of urea is 60, and 28 grams of nitrogen are present in a gm mole of urea. As the relationship between urea and BUN is 60/28, BUN can be converted to urea by multiplying BUN by 2.14, i.e. the real concentration of urea is BUN × (60/28).
Urea is completely filtered by the glomeruli, and about 30-40% of the filtered amount is reabsorbed in the renal tubules depending on the person’s state of hydration.
Blood level of urea is affected by a number of non-renal factors (e.g. high protein diet, upper gastrointestinal hemorrhage, liver function, etc.) and therefore utility of BUN as an indicator of renal function is limited. Also considerable destruction of renal parenchyma is required before elevation of blood urea can occur.
The term azotemia refers to the increase in the blood level of urea; uremia is the clinical syndrome resulting from this increase. If renal function is absent, BUN rises by 10-20 mg/dl/day.
Causes of increased BUN:
- Pre-renal azotemia: shock, congestive heart failure, salt and water depletion
- Renal azotemia: impairment of renal function
- Post-renal azotemia: obstruction of urinary tract
- Increased rate of production of urea:
• High protein diet
• Increased protein catabolism (trauma, burns, fever)
• Absorption of amino acids and peptides from a large gastrointestinal hemorrhage or tissue hematoma
Methods for estimation of BUN:
Two methods are commonly used.
- Diacetyl monoxime urea method: This is a direct method. Urea reacts with diacetyl monoxime at high temperature in the presence of a strong acid and an oxidizing agent. Reaction of urea and diacetyl monoxime produces a yellow diazine derivative. The intensity of color is measured in a colorimeter or spectrophotometer.
- Urease- Berthelot reaction: This is an indirect method. Enzyme urease splits off ammonia from the urea molecule at 37°C. Ammonia generated is then reacted with alkaline hypochlorite and phenol with a catalyst to produce a stable color (indophenol). Intensity of color produced is then measured in a spectrophotometer at 570 nm.
Reference range for BUN in adults is 7-18 mg/dl. In adults > 60 years, level is 8-21 mg/dl.
Creatinine is a nitrogenous waste product formed in muscle from creatine phosphate. Endogenous production of creatinine is proportional to muscle mass and body weight. Exogenous creatinine (from ingestion of meat) has little effect on daily creatinine excretion.
Serum creatinine is a more specific and more sensitive indicator of renal function as compared to BUN because:
- It is produced from muscles at a constant rate and its level in blood is not affected by diet, protein catabolism, or other exogenous factors;
- It is not reabsorbed, and very little is secreted by tubules.
With muscle mass remaining constant, increased creatinine level reflects reduction of glomerular filtration rate. However, because of significant kidney reserve, increase of serum creatinine level (from 1.0 mg/dl to 2.0 mg/dl) in blood does not occur until about 50% of kidney function is lost. Therefore, serum creatinine is not a sensitive indicator of early renal impairment. Also, laboratory report showing serum creatinine “within normal range” does not necessarily mean that the level is normal; the level should be correlated with body weight, age, and sex of the individual. If renal function is absent, serum creatinine rises by 1.0 to 1.5 mg/dl/day (Figure 842.2).
Figure 842.2 Relationship between glomerular filtration rate and serum creatinine. Significant increase of serum creatinine does not occur till a considerable fall in GFR
Causes of Increased Serum Creatinine Level
- Pre-renal, renal, and post-renal azotemia
- Large amount of dietary meat
- Active acromegaly and gigantism
Causes of Decreased Serum Creatinine Level
- Increasing age (reduction in muscle mass)
Methods for Estimation of Serum Creatinine
The test for serum creatinine is cheap, readily available, and simple to perform. There are two methods that are commonly used:
- Jaffe’s reaction (Alkaline picrate reaction): This is the most widely used method. Creatinine reacts with picrate in an alkaline solution to produce spectrophotometer at 485 nm. Certain substances in plasma (such as glucose, protein, fructose, ascorbic acid, acetoacetate, acetone, and cephalosporins) react with picrate in a similar manner; these are called as non-creatinine chromogens (and can cause false elevation of serum creatinine level). Thus ‘true’ creatinine is less by 0.2 to 0.4 mg/dl when estimated by Jaffe’s reaction.
- Enzymatic methods: These methods use enzymes that cleave creatinine; hydrogen peroxide produced then reacts with phenol and a dye to produce a colored product, which is measured in a spectrophotometer.
Adult males: 0.7-1.3 mg/dl.
Adult females: 0.6-1.1 mg/dl.
Serum creatinine alone should not be used to assess renal function. This is because serum creatinine concentration depends on age, sex, muscle mass, glomerular filtration and amount of tubular secretion. Thus, normal serum creatinine range is wide. Serum creatinine begins to rise when GFR falls below 50% of normal. Minor rise of serum creatinine is associated with significant reduction of GFR (Figure 842.2). Therefore early stage of chronic renal impairment cannot be detected by measurement of serum creatinine alone.
BUN/Serum Creatinine Ratio
Clinicians commonly calculate BUN/creatinine ratio to discriminate pre-renal and post-renal azotemia from renal azotemia. Normal ratio is 12:1 to 20:1.
Causes of Increased BUN/Creatinine Ratio (>20:1):
- Increased BUN with normal serum creatinine:
• Pre-renal azotemia (reduced renal perfusion)
• High protein diet
• Increased protein catabolism
• Gastrointestinal hemorrhage
- Increase of both BUN and serum creatinine with disproportionately greater increase of BUN:
• Post-renal azotemia (Obstruction to the outflow of urine)
Obstruction to the urine outflow causes diffusion of urinary urea back into the blood from tubules because of backpressure.
Causes of Decreased BUN/Creatinine Ratio (<10:1)
- Acute tubular necrosis
- Low protein diet, starvation
- Severe liver disease
One can estimate GFR from age, sex, body weight, and serum creatinine value of a person from the following formula (Cockcroft and Gault):
Creatinine clearance in ml/min = (140 - Age in years) × (Body weight in kg)
(72 × Serum creatinine in mg/dl)
(72 × Serum creatinine in mg/dl)
In females, the value obtained from above equation is multiplied by 0.85 to get the result.
It is recommended by National Kidney Foundation (USA) to calculate creatinine clearance by Cockcroft and Gault or other equation from serum creatinine value rather than estimating creatinine clearance from a 24-hour urine sample. This is because the latter test is inconvenient, time-consuming, and often inaccurate.