Fecal Analysis
100-200 g
amount of feces normally passed each day
small instestine
digests and absorbs foodstuffs
large intestine
absorbs water, sodium and chloride
diarrhea
an increase in volume, liquidity, and frequency of bowel movements compared with individual's normal pattern
secretory
increased solute secretions by intestine draws water and electrolytes into intestine
osmotic
increased osmotically active solutes draw water and electrolytes into intestine
intestinal hypermotility
decreases time available for absorption; can occur alone or with secretory or osmotic
enterotoxin-producing organisms and damage to mucosa due to drugs or disease
secretory causes
maldigestion or malabsorption
osmotic causes
maldigestion
inability to convert foodstuffs into readily abailable absorbable substances
malabsorption
normal digestive ability, but inadequate intestinal absorption of already processed foodstuffs
abdominal distention stimulates motility; laxatives, stress, drugs or other diarrheas
intestinal hypermotility causes
steatorrhea
fecal fat excretion greater than 7g/day
malabsorption syndrome features
feces are pale, greasy, spongy, or pasty and very foul smelling
contamination
should be avoided in specimen collection
bile pigments (urobilins)
cause normal brown color of stool
formed cylindrical masses
normal consistency and form
mucus
not normally present in feces; associated with many conditions
metabolic by-products of intestinal flora bacteria
causes normal odor
white blood cells
not normally present; smallest amount indicates invasive or inflammatory condition of intestinal wall
lactoferrin
protein present in activated neutrophils; detected through immuno-based tests
fecal fat
qualitative orange-red staining of neutral fats with Sudan 3 or 4 or oil red O; detects total fats
meat fibers
can be seen on fecal fat slides; increase is abnormal
occult blood
small amount in feces and is not visualy apparent; any increase is always significant
osmotic
increased active solutes draw water and electrolytes into intestine
bright red stools
can indicate bleeding in the lower GI tract
dark or mahogany or black stools (melena)
can indicate bleeding in upper GI tract
Guaiac-based occult blood testing
based on pseudoperoxidase activity of hemoglobin resulting in color change
immunochemical occult blood testing
based on reaction of polyclonal antihuman antibodies to globin portion of undegraded hemoglobin
porphyrin-based occult blood testing
based on chemical conversion of heme to fluorescent porphyrins
Apt test for fetal hemoglobin
used to differentiate between fetal and maternal blood in newborn's stool; qualitative based on alkaline resistance of fetal hemoglobin
quantitative fecal fat
definitive test for steatorrhea