General stool examination

Stool (or feces) is usually thought of as nothing but waste — something to quickly flush away. But bowel movements can provide doctors with valuable information as to what's wrong when a child has a problem in the stomach, intestines, or another part of the gastrointestinal system.

A doctor may order a stool collection to test for a variety of possible conditions, including:

1. allergy or inflammation in the body, such as part of the evaluation of milk protein allergy in infants
2. infection, as caused by some types of bacteria, viruses, or parasites that invade the gastrointestinal system
3. digestive problems, such as the malabsorption of certain sugars, fats, or nutrients bleeding inside of the gastrointestinal tract

The most common reason to test stool is to determine whether a type of bacteria or parasite may be infecting the intestines. Many microscopic organisms living in the intestines are necessary for normal digestion. If the intestines become infected with harmful bacteria or parasites, though, it can cause problems like certain types of bloody diarrhea, and testing stool can help find the cause.Stool samples are also sometimes analyzed for what they contain; for instance, examining the fat content. Normally, fat is completely absorbed from the intestine, and the stool contains virtually no fat. In certain types of digestive disorders, however, fat is incompletely absorbed and remains in the stool.

Stool test

A stool test is one where fecal matter is collected for analysis to diagnose the presence or absence of a medical condition.

Fecal occult blood test

Fecal occult blood (FOB) refers to blood in the feces that is not visibly apparent. A fecal occult blood test (FOBT) checks for hidden (occult) blood in the stool (feces). Newer tests look for globin, DNA, or other blood factors including transferrin, while conventional stool guaiac tests look for heme. Fecal occult blood testing (FOBT), as its name implies, aims to detect subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon. Positive tests ("positive stool") may result from either upper gastrointestinal bleeding or lower gastrointestinal bleeding and warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer). The test does not directly detect colon cancer but is often used in clinical screening for that disease, but it can also be used to look for active occult blood loss in anemia or when there are gastrointestinal symptoms.

Methodology

There are four methods in clinical use for testing for occult blood in feces. These look at different properties, such as heme, globin, and porphyrins in blood or at DNA from cellular material such as from lesions of the intestinal mucosa.

- Stool guaiac test for fecal occult blood (gFOBT): - The stool guaiac testinvolves       smearing some feces on to some absorbent paper that has been treated with a chemical.

- Fecal Immunochemical Testing (FIT), and immunochemical fecal occult blood test (iFOBT): - which chemically depend on specific antibodies to detect globin.

- Fecal porphyrin quantification: - HemoQuant, unlike gFOBT and FIT, permits precise quantification of hemoglobin, and is analytically validated with gastric juice and urine, as well as stool samples.

- Fecal DNA test : - test extracts human DNA from the stool sample and tests it for alterations that have been associated with cancer.

- Additional methods of looking for occult blood are being explored, including transferrin dipstick and stool cytology.

Microbiology tests

Parasitic diseases such as Ascariasis, Hookworm, Strongyloidiasis and Whipworm can be diagnosed by examining stools under a microscope for the presence of worm larvae or eggs. Some bacterial diseases can be detected with a stool culture. Toxins from bacteria such as Clostridium difficile ('C. diff.') can also be identified. Viruses such as rotavirus can also be found in stools.

Chemical tests

A fecal pH test may be used determine lactose intolerance or the presence of an infection. Steatorrhea can be diagnosed using a Fecal fat test that checks for the malabsorption of fat. Faecal Elastase levels are becoming the mainstay of pancreatitis diagnosis.

Fecal pH test

A fecal pH test is one where a specimen of feces is tested for acidity in order to diagnose a medical condition. Human feces is normally alkaline. An acidic stool can indicate a digestive problem such as lactose intolerance or a contagion such as E. coli or Rotavirus.

Test procedure

The test is fast and can be performed in a doctor's office. A patient must not be receiving antibiotics. At least half a milliliter of feces is collected and a strip of nitrazine paper is dipped in the sample and compared against a color scale. A pH of less than 5.5 indicates an acidic sample.

Fecal fat test

fecal fat test is a diagnostic test for fat malabsorption conditions, which lead to excess fat in the feces(steatorrhea). In the small intestine, dietary fat (primarily triglycerides) is digested by enzymes such as pancreatic lipase into smaller molecules which can be absorbed through the wall of the small intestine and enter the circulation for metabolism and storage. As fat is a valuable nutrient, human feces normally contain very little undigested fat. However, a number of diseases of the pancreas and gastrointestinal tract are characterized by fat malabsorption.

Examples of such diseases are:

- disorders of exocrine pancreatic function, such as chronic pancreatitis, cystic fibrosis and Shwachman-Diamond syndrome (these are characterized by deficiency of pancreatic digestive enzymes)

- celiac disease (in which the fat malabsorption in severe cases is due to inflammatory damage to the integrity of the intestinal lining)

- short bowel syndrome (in which much of the small intestine has had to be surgically removed and the remaining portion cannot completely absorb all of the fat).

- small bowel bacterial overgrowth syndrome

Microscopy

In the simplest form of the fecal fat test, a random fecal specimen is submitted to the hospital laboratory and examined under a microscope after staining with a Sudan III or Sudan IV dye ("Sudan staining"). Visible amounts of fat indicate some degree of fat malabsorption.

Quantitative fecal fat test

Quantitative fecal fat tests measure and report an amount of fat. This usually done over a period of three days, the patient collecting all of their feces into a container.

The container is thoroughly mixed to homogenize the feces, this can be done with a paint mixer. A small sample from the feces is collected. The fat content is extracted with solvents and measured by saponification (turning the fat into soap).

Normally up to 7 grams of fat can be malabsorbed in people consuming 100 grams of fat per day. In patients with diarrhea, up to 12 grams of fat may be malabsorbed since the presence of diarrhea interferes with fat absorption, even when the diarrhea is not due to fat malabsorption.

Stool Analysis Results

Normal:

The stool appears brown, soft, and well-formed in consistency.

No blood, mucus, pus, bacteria, viruses, fungi, or parasites are present in the stool.

The shape of the stool is tubular, reflecting its passage through the colon.

Normal pH of stool is about 6.

Less than 2 milligrams per gram (mg/g) of certain sugars called reducing factors are present in the stool.

Abnormal:

Increased volume of stool may indicate poor absorption of fats.

Blood, mucus, pus, bacteria, viruses, fungi, or parasites are present in the stool.

Low levels of certain enzymes (such as trypsin or elastase) may be present.

Reducing factors levels between 2 and 5 mg/g are considered borderline. Levels greater than 5 mg/g are abnormal.

Abnormal values may mean

- High levels of fat in the stool may indicate chronic pancreatitis, Crohn's disease, or cystic fibrosis.

- The presence of undigested meat fibers in the stool may indicate pancreatitis.

- An abnormal pH may indicate poor absorption of carbohydrates or fat.

- Low levels of certain enzymes (such as trypsin or elastase) may indicate digestive complications of cystic fibrosis or pancreatic insufficiency.

- The presence of blood in the stool indicates bleeding in the digestive tract.

- The presence of white blood cells in the stool may indicate bacterial diarrhea. A       specific

organism may be identified.

- Rotaviruses are a common cause of diarrhea in young children. If diarrhea is present, testing may be done to determine the presence of rotaviruses in the stool.

High levels of reducing factors in the stool may indicate a problem digesting certain sugars (especially sucrose and lactase).