Chapter 10 Fecal Analysis Flashcards
What is fecal analysis used to detect
GI bleeding, liver and biliary duct disorders, pancreatic disorders malabsorption syndromes, maldigestion, and infections
Fecal specimen contain what 8 things
Bacteria, cellulose, undigested foodstuffs, GI secretions, bile pigments, cells from the intestinal walls, electrolytes, water
How much feces is extracted in a 24-hour period?
100 to 200g
What is the primary site for the final breakdown and reabsorption of proteins, carbohydrates, and fats
Small intestine
What is the site of water, sodium, and chloride absorption
Large intestine
About how much ingested fluid, saliva, gastric, liver, pancreatic, and intestinal secretions enter the digestive tract each day
9000 mL
How much excess water causes diarrhea
> 3000 mL
What causes constipation?
Increased water absorption in large intestine with decreased bowel motility
> 200 g stool weight per day with increased liquid and more than 3 movements per day
Diarrhea
Chronic diarrhea duration
> 4 weeks
Acute diarrhea duration
<4 weeks
Mechanisms of diarrhea
Secretory, osmotic, altered motility
Lab tests for diarrhea
Fecal electrolytes, osmolality, and pH
Diarrhea pH <5.6 indicates
Sugar malabsorption
What is used to calculate fecal osmotic gap for diarrhea
Sodium, potassium, osmolality
Increased solute secretions by intestines cause increase secretion of water and electrolytes to large intestines causes
Secretory diarrhea
Secretory diarrhea bacterial, viral, and protozoan infections
E. coli, clostridium, Vibrio cholerae, salmonella, shigella, staphylococcus, campylobacter, cryptosporidium
Other causes of secretory diarrhea
Drugs, laxatives, inflammatory bowel diseases/colitis, endocrine disorders, malignancy, collagen vascular disease
Poor absorption that exerts osmotic pressure across the intestinal mucosa
Osmotic diarrhea
What causes osmotic diarrhea
Incomplete digestion of reabsorption of food increases water retention in large intestine
Impaired digestion of foods
Maldigestion
Impaired reabsorption
Malabsorption
What causes osmotic diarrhea (7)
Lactose intolerance, celiac sprue (malabsorption), amebiasis, giardiasis, antibiotics, laxatives, antacids
Hypermotility and constipation; food, chemicals, stress, and exercises are causes of
Irritable bowel syndrome (IBS)
Altered motility: <35 minutes
Rapid gastric emptying (RGE; dumping syndrome)
Early dumping syndrome
10 to 30 minutes
Late dumping syndrome
2 to 3 hours
Causes of altered motility (5)
Gastrectomy, gastric bypass, postvagotomy, duodenal ulcer, diabetes mellitus
Increased fats in the stool >7 g/day. Pancreatic insufficiency and malabsorption and lack of bile salts (triglyceride digestion)
Steatorrhea
Causes of steatorrhea (3)
Cystic fibrosis, pancreatitis, and malignancy decrease pancreatic enzymes for lipid breakdown
Physical appearance of steatorrhea feces
Pale, greasy, bulky, foul odor
What kind of containers are used for feces collection
Ova and parasite containers
How long are quantitative collections?
72 hours
Color and consistency of stool: upper GI bleeding; iron therapy
Black tarry stool
Color and consistency of stool: lower GI bleeding
Red stool
Color and consistency of stool: fat malabsorption
Steatorrhea (greasy, spongy)
Color and consistency of stool: watery fecal material
Diarrhea
Color and consistency of stool: bowel obstruction
Ribbon like stools
Color and consistency of stool: inflammation of intestinal wall (colitis)
Mucus
Color and consistency of stool: bile-duct obstruction, obstructive jaundice
Clay-colored; pale
Name the type of fecal analysis
Significance: determine cause of diarrhea
Neutrophils: bacterial intestinal wall infections, ulcerative colitis, accesses
No neutrophils: toxin producing bacteria, viruses, and parasites
Fecal leukocytes
Name the type of fecal analysis
Significance: detects fat malabsorption disorders by staining with Sudan III or oil red O. Look for increased fat droplets/hpf. Steatorrhea >60 droplets/hpf
Fecal fat
Name the type of fecal analysis
Significance: look for undigested striated muscle fibers
Muscle/meat fibers
Name the type of fecal analysis
Significance: used in early detection of colorectal cancer.
Ortho-toluidine method based on pseudoperoxidase activity of hemoglobin.
Immunological methods
Occult blood (GFOBT or IFOBT)
Sudan III stain for fecal fats
Occult blood slide
APT test for fetal hemoglobin test step 1
Checking bloody stools and vomit from neonates who may have swallowed maternal blood during delivery
APT test for fetal hemoglobin test step 2
Emulsify material in water to release Hgb
APT test for fetal hemoglobin test step 3
Centrifuge, add 1% NaOH to pink supernatant
Pink color remains = alkali-resistant fetal Hgb
Yellow-brown = maternal Hgb
High Hgb =
Maternal thalassemia
Definitive test for steatorrhea
Quantitative fecal fat
Patient requirements for quantitative fecal fat test
Limit fat intake for 3 days before
Avoid laxatives, fat substitute, oils, creams, lubricants
Collect feces for 2-3 days
How does CLS test quantitative fecal fat
Weigh, emulsify and aliquot for liquid testing
Common fecal testing on infants for disaccharidase deficiencies and lactose intolerance in adults
Fecal carbohydrate tests
Why is pH tested in fecal carbohydrate tests
To detect fermentation of excess carbohydrates by intestinal bacteria
What is normal stool pH and what does pH below 5.5 indicate?
Normal pH =7 to 8
Below 5.5 indicates increased carbohydrates
Describe the Clinitest and an abnormal result
One part stool in two parts water; emulsify and perform test
> 250 mg/dL is abnormal
Inadequate intestinal absorption can cause
Excess carbohydrate in feces
Xylose test tests for
Malabsorption
Low level of D-xylose in urine indicates
Malabsorption
D-xylose does not need to be digested but must be reabsorbed to appear in urine
