Chronic diarrhea

DDx

Common

  • Irritable bowel syndrome, lactase deficiency, parasites, caffeine, alcohol, laxative abuse
Osmotic
  • Lactase deficiency
  • Medications: antacids, lactulose, sorbitol, Olestra
  • Factitious: magnesium-containing antacids or laxatives
Secretory
  • Hormonal: Zollinger-Ellison syndrome (gastrinoma), carcinoid, VIPoma, medullary thyroid carcinoma
  • Laxative abuse: phenolphthalein, cascara, senna
  • Villous adenoma
  • Medications
Inflammatory conditions
  • Inflammatory bowel disease
  • Microscopic colitis (lymphocytic or collagenous)
  • Cancer with obstruction and pseudodiarrhea
  • Radiation colitis
Malabsorption
  • Small bowel: celiac sprue, Whipple's disease, tropical sprue, eosinophilic gastroenteritis, small bowel resection, Crohn's disease
  • Lymphatic obstruction: lymphoma, carcinoid, tuberculosis, Mycobacterium avium complex (MAC), Kaposi's sarcoma, sarcoidosis, retroperitoneal fibrosis
  • Pancreatic insufficiency: chronic pancreatitis, cystic fibrosis, pancreatic cancer
  • Bacterial overgrowth, eg, diabetes
  • Reduced bile salts: ileal resection, Crohn's disease, postcholecystectomy
Motility disorders
  • Irritable bowel syndrome
  • Postsurgical: vagotomy, partial gastrectomy, blind loop with bacterial overgrowth
  • Systemic disease: diabetes mellitus, hyperthyroidism, scleroderma
  • Caffeine or alcohol use
Chronic infections
  • Parasites: giardiasis, amebiasis, strongyloidiasis
Other
  • Ischemic colitis
  • Adrenal insufficiency

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