Internal Medicine

P1: RLJ/OZN P2: KUF

0521779407-D-01 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 7:41

Diarrhea 483

tests

Laboratory

Basic Studies: Blood

■CBC, LFTs, BUN, creatinine, TSH/FT4, chem 7, albumin, calcium,

ESR

Basic Studies: Stool

■Fecal leukocytes, O&P, C&S, stool hemocult, C. difficile toxin, quali-

tative fecal fat

Specific Diagnostic Tests (Mostly for Chronic Diarrhea)

■1. 72 hr quantitative stool collection: evaluate weight, fat, osmolality,

■electrolytes, Mg, pH, occult blood, laxative screen, and/or fecal

■chymotrypsin

➣Quantitative fecal fat 7–14 gm/d: low specificity for accurate diag-

nosis between defective fat digestion and absorption, >14 g/d:

more specific for exocrine pancreatic disease, small intestinal

mucosal defects, abnormal enterohepatic bile salt circulation

➣Stool electrolytes to calculate osmotic gap: 290–2([Na]+[K])

if >125, pure osmotic diarrhea; if <50, pure secretory diarrhea

➣Fecal pH <5.3 carbohydrate malabsorption, >5.6 factors other

than carbohydrate malabsorption present

➣Phenolphthalein test: red discolorization after alkylinization in

laxative use

■Urine for 5-HIAA, VMA and metanephrine, serum for gastrin, VIP,

PP, calcitonin: detection of hormone producing tumors

■Endoscopy

➣Small/large intestinal biopsy: colitis, tumor, malabsorption,

pseudomembranes, melanosis coli

➣Small intestinal aspirate: bacterial overgrowth≥10 colonies/ml

➣Barium radiographs (UGI/SBFT) may complement endoscopy

■Lactose-free diet trial/lactose and other carbohydrate H2 breath

tests

■Therapeutic trial of cholestyramine or pancreatic enzymes, specific

bile acid absorption tests or exocrine pancreatic function tests

differential diagnosis

Exudative/Inflammatory Diarrhea

■IBD, microscopic colitis, infectious diarrheas with invasive organ-

isms, radiation enteritis, ischemic colitis, food allergy, food toxins