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Fecal Analysis

MEDT 208 Urinalysis: fecal analysis study objectives

QuestionAnswer
What is the mechanism of secretory diarrhea? Increased intestinal secretion of solute causes increased fluid volume in large intestine; exceeds absorptive threshold of large intestine.
What is the mechanism of osmotic diarrhea? Ingestion of large quantity of osmotically active solutes causes additional excretion of water & electrolytes into lumen. Fluid volume exceeds threshold of large intestine. (Increased osmotic gap).
How are maldigestion & malabsorption related to diarrhea? Both result in abnormally increased qty of food to large intestine. Food is osmotically active, which cause retention of large qty water and electrolytes in intestinal lumen = diarrhea.
What is maldigestion? Inability to convert food into readily absorbable substances. Pancreatic digestive enzymes or bile salts for fat emulsion & lipase activation missing/deficient.
What is malabsorption? Normal digestive ability w/inadequate intestinal absorption of pre-processed foods.
What is the osmolar gap? The difference between measured & calculated fecal osmolality.
What is the osmolar gap value for osmotic diarrhea? > 20 mOsm/kg
What is the osmolar gap value for secretory diarrhea? 10-20 mOsm/kg
What are the macroscopic features of normal feces? Brown, formed, unremarkable odor, cylindrical or tubular shape.
What causes clay, gray, pale or white stool? Post-hepatic obstruction OR barium
What causes red stool? Blood (lower GI), beets, food dye, drugs
What causes black stool? Blood from upper GI, Iron, charcoal, bismuth
What causes green stool? Green veggies, biliverdin (antibiotic therapy)
What causes hard stools? Constipation/dehydration
What causes soft stools? Increased fecal water content
What causes watery stools? Diarrhea, steatorrhea
What causes narrow, ribbon-like stools? Bowel obstruction
What causes small, round stools? Constipation
What causes bulky stools? Steatorrhea
What is the primary purpose of the microscopic examination for fecal leukocytes? differential diagnosis of diarrhea; or detect invasive, inflammatory conditions.
What is the basic procedure for qualitative assessment of fecal fat using a microscopic examination? Increased fat seen macroscopically, confirmed microscopically with Sudan III or IV, oil red O stains.
What color do neutral fecal fats stain? red-orange
What is the clinical utility of quantitative fecal fat tests? Screening for steatorrhea.
Which fecal fats are present in maldigestion? Increased neutral fats
Which fecal fats are present in malabsorption? Normal fats + Increased total fats
List at least five causes of blood in feces. (1) Colorectal cancer; (2) Aspirin and anti-inflammatory medications; (3) Red meat; (4) Horseradish, raw broccoli, cauliflower, radishes, turnips; (5) Melons; (6) Menstrual and hemorrhoid contamination
Why is detection of fecal occult blood important, and what is it recommended for? Importance of fecal occult blood detection: recommended annual screening for colorectal cancer.
What is the principle of the Guiac-based test for fecal occult blood? Pseudoperoxidase activity of hemoglobin.
What is the principal of the Immmunochemical test for fecal blood? Polyclonal antibodies
What is the principle of the Apt test (fetal hemoglobin)? Alkaline resistance of fetal hemoglobin. In alkaline media, F-hemoglobin reacts differently than adult hemoglobin.
What is the key sample requirement for the Apt test? MUST contain fresh blood.
A pink supernatant in the Apt test indicates? alkali-resistant fetal Hgb b/c not degraded by NaOH.
A yellow-brown supernatant in the Apt test indicates? Maternal Hgb present, degraded by NaOH
What effect does disaccharidase deficiency has on fecal characteristics and formation? Results in bacterial fermentation of disaccharides, which causes production of large amounts of intestinal gas, diarrheal stools w/characteristic decreased pH (5.0/6.0).
State two methods for the qualitative detection of abnormal quantities of fecal carbohydrates. (1) Clinitest (presence of carbs/reducing sugars); (2)Rapid qualitative fecal pH (carbs --> characteristically reduced pH 5.0-6.0)
What is the purpose of the xylose absorption test? Differentiate carb metabolism VS. carb maldigestion.
What is the principle of the xylose absorption test? D-xylose is normally easily absorbed by the intestines. When problems with absorption occur, D-xylose is not absorbed by the intestines, and its level in blood and urine is low.
How can the presence of steatorrhea be screened for by testing a random stool sample? Sudan III staining
What confirmatory test should be performed for steatorrhea? quantitative fecal fat
Describe the appearance of the stool specimens if steatorrhea is present. Bulky, frothy
If a pancreatic insufficiency is suspected,  what two  tests that can be performed on a stool specimen to aid in the diagnosis. Chymotrypsin and elastase 1
What diagnostic tests or procedures are used to diagnose cystic fibrosis?  CF mutation panel; Sweat chloride; Nasal (transepithelial) Potential Difference (NPD)
A 70-year-old woman suffering from arthritis takes the occult blood screening test as part of a routine physical. The results of all three specimens are positive for occult blood. What's a possible nonpatholgic cause for the unexpected results? Patient is taking large amounts of aspirin
Bob is a 50-year-old man advised by the doctor to lose 30 lb. He has been doing well on a high-protein, low carbohydrate diet. Two of his three specimens are positive for occult blood. What is a possible nonpathologic cause for the unexpected results? Bob is eating primarily red meat
A watery black stool from a neonate is received in the laboratory with requests for an Apt test, fecal pH, and a Clinitest.  Which of these tests can not be performed on this specimen? (Apt, Clinitest, Fecal pH)  Apt  (hemoglobin already denatured)
What is a possible cause of black stool in infants? Infant ingested maternal blood
Which of the following tests is not performed to detect osmotic diarrhea? (Flintiest, fecal fats, fecal neutrophils, muscle fibers) Muscle fibers
What is the fecal test that requires a 3-day specimen? (Fecal occult blood, APT test, Elastase I, Quantitative fecal fat testing) Quantitative fecal fat testing
Large orange-red droplets seen on direct microscopic examination of stools mixed with Sudan Ill represent: Neutral fats
The term "occult" blood describes blood that: Is not visibly apparent in the stool specimen
What is the recommended number of samples that should be tested to screen for occult blood result? Two samples taken from different parts of three stools
Which test is the most sensitive to upper Gl bleeding? Hemoquant
Annual testing for fecal occult blood has a high predictive value for the detection of: Colorectal cancer
Tests for the detection of "occult" blood rely on the: Pseudoperoxidase activity of hemoglobin
What is the significance of an APT test that remains pink after addition of sodium hydroxide? Fetal hemoglobin is present.
Created by: 100002485764648