(>4 wk) (Nejm 1995;332:725) (Table 6.5)

Cause:In order of frequency: chronic infection, inflammatory and irritable bowel disease, steatorrhea, carbohydrate malabsorption, medications/food additives, previous surgery w bacterial overgrowth, endocrine (adrenal insufficiency, hyper/hypothyroidism, diabetes mellitus), laxative abuse, ischemic bowel, radiation enteritis, colon cancer, idiopathic/functional, microscopic colitis (Am J Med 2000;108:416) from either collagenous or lymphocytic colitis, which presents as chronic watery diarrhea, have a normal-appearing mucosa on endoscopy but abnl pathlogy on bx

Pathophys:Bacterial gut wall invasion; enterotoxin production; bacterial adherence to epithelial cell membrane cytotoxin production; unabsorbed solutes causing osmotic diarrhea; deconjugated bile salts and hydroxylated fatty acids; congenital/familial absorptive/secretory abnormalities; Zollinger-Ellison syndrome, vasoactive intestinal peptide, calcitonin, carcinoid tumors; diabetic autonomic neuropathy; factitious from laxative use, or water dilution of stool (Nejm 1994;330:1418)

of idiopathic diarrhea, if w/u neg, is benign and resolves in <4 yr (Nejm 1992;327:1849)

Lab:

Chem:Lytes, BUN/creat, TSH, T₄, gastrin, VIP if >1 L/d

Hem:CBC, ESR

Endo:sigmoid/colonoscopy w bx

Stool:for fecal leukocytes, O⁺P × 3 before barium studies, pH, 24 h weight, 72 h fat

Xray:Endoscopy, CT

Rx: Tailor tx to cause; generally the following are employed: somatostatin analog octreotide (Ann IM 1991;115:705); verapamil; loperamide (Imodium) 2-mg tabs up to 8 qd in adults; cholestyramine; antibiotics