Fecalysis

• Fecal analysis is a routine microbiology and chemical test of stool.
• Early detection of GIT bleeding can be done through an occult blood test used to check stool samples for hidden blood.
• Fecal immunochemical test (FIT) uses antibodies to detect blood in the stool.
• Fecal analysis can detect liver and biliary duct disorder.
• Maldigestion and malabsorption syndrome can be indicated through fecal analysis.
• Fecal analysis can indicate inflammation.
• Lactose tolerance test involves measuring the amount of glucose in the bloodstream two hours after drinking a liquid that contains high levels of lactose.
• If the glucose level doesn't rise, it indicates that the body isn't properly digesting and absorbing the lactose-filled drink.
• Fecal analysis can be used to determine causes of steatorrhea and diarrhea.
• Detection and identification of pathogens can be done through fecal analysis.
• Undigested food, cellulose-complex carbohydrates, bacteria, gastrointestinal secretions, bile pigments, cells from intestinal wall, water, and electrolytes are major constituents of stool.
• The liver produces bile for emulsification of fats, the gall bladder stores bile, and the pancreas produces pancreatic juices (trypsin, chymotrypsin, lipase and amino peptidase).
• Diarrhea should have a stool weight of >200 grams, increased liquidity, and frequency of >3 times per day.
• Factors contributing to diarrhea include duration of illness, mechanism, severity, stool characteristics, and classification.
• Secretory diarrhea is caused by increased solute secretion by the intestine and can be due to enterotoxin-producing organisms.
• Osmotic diarrhea is caused by increased amounts of osmotically active solutes remaining in the lumen and can be due to lactose intolerance, celiac sprue, or poor absorption of sugars.
• Altered motility diarrhea is seen in irritable bowel syndrome and can cause bloating, increased flatus, diarrhea or constipation.
• Steatorrhea is caused by the absence of bile salts and pancreatic lipase, which aid in the digestion of fat via fat emulsification, and is characterized by >6 grams per day stool fats, increased levels of fat in the stool, and a "rotten-egg odor".
• Creatorrhea is the presence of undigested muscle fibers in feces.
• Carbohydrates lower the pH of stool to <5.5 (lactose intolerance), with a normal stool having a pH of 7.8 (alkaline).
• Cholesterol is detected by formation of crystals.
• Occult blood is detected by pseudoperoxidase activity of haemoglobin, with a positive result indicated by blue color.
• Carbohydrates are used for diagnosis of osmotic diarrhea and are most valuable in assessing cases of infant diarrhea.
• Fecal enzymes are also regulated in patients with thalassemia major, as high concentration of hemoglobin F (HbF) can cause false positive results.
• Guaiac test is the least sensitive but the most preferred test for occult blood.
• Fecal fats are quantitative fats tests that require a 3-day collection of stool and are confirmatory for steatorrhea.
• Chymotrypsin is assessed through gelatin hydrolysis or spectrophotometry.
• Fecal fats are qualitative fats tests used for screening of steatorrhea and monitoring treatment and malabsorption conditions.
• D-xylose is used in malabsorption test to check how well the intestines absorb a simple sugar (D-xylose).
• Copper reduction test is used in clinitext to distinguish between maternal and fetal blood in cases of meconium stains.
• Trypsin is assessed through ingestion of gelatin in x-ray paper after addition of emulsified stool.
• Benzidine and o-toluidine produce blue color if positive, making them the most sensitive test for occult blood.
• Fecal enzymes are regulated, with a maximum intake of 100 gm fats/day, prior to and during collection.
• Fecal fats are also qualitative fats tests that use Sudan III as the most routinely used dye.
• Neutral fats are stained with Sudan III and a finding of more than 60 orange red droplets usually at the edge of the coverslip indicates steatorrhea.
• Elastase I is assessed through APT test/hemoglobin alkaline denaturation.
• Fecal enzymes are enzymes derived from the pancreas needed for digestion and are used in the diagnosis of chronic pancreatitis, steatorrhea and cystic fibrosis.
• Split-fat stain involves adding acetic acid to stain Sudan III and the acetic acid will hydrolyze the fatty acids and fatty acid salts.
• Melena is black, tarry feces associated with GI bleeding.
• Stool odor is due to bacterial fermentation of carbohydrates.