Causes of Chronic Diarrhea
Osmotic Diarrhea
 1. Medications: antacids, lactulose, sorbitol
 2. Disaccharidase deficiency: lactose intolerance
 3. Factitious diarrhea: magnesium (antacids, laxatives)
Secretory diarrhea
 1. Hormonally mediated: VIPoma, carcinoid, medullary carcinoma of thyroid (calcitonin), Zollinger-Ellison syndrome (gastrin)
 2. Factitious diarrhea (laxative abuse); phenolphthalein, cascara, senna
 3. Villous adenoma
 4. Bile salt malabsorption (idiopathic, ileal resection; Crohn ileitis; postcholecystectomy)
 5. Medications
Inflammatory conditions
 1. Ulcerative colitis
 2. Crohn disease
 3. Microscopic colitis
 4. Malignancy: lymphoma, adenocarcinoma (with obstruction and pseudodiarrhea)
 5. Radiation enteritis
Malabsorption syndromes
 1. Small bowel mucosal disorders: celiac sprue, tropical sprue, Whipple disease, eosinophilic gastroenteritis, small bowel resection (short bowel syndrome), Crohn disease
 2. Lymphatic obstruction: lymphoma, carcinoid, infectious (tuberculosis, MAI), Kaposi sarcoma, sarcoidosis, retroperitoneal fibrosis
 3. Pancreatic disease: chronic pancreatitis, pancreatic carcinoma
 4. Bacterial overgrowth: motility disorders (diabetes, vagotomy), scleroderma, fistulas, small intestinal diverticula
Motility disorders
 1. Postsurgical: vagotomy, partial gastrectomy, blind loop with bacterial overgrowth
 2. Systemic disorders: scleroderma, diabetes mellitus, hyperthyroidism
 3. Irritable bowel syndrome
Chronic infections
 1. Parasites: Giardia lamblia, Entamoeba histolytica, Strongyloidiasis stercoralis, Capillaria philippinensis
 2. AIDS-related: Viral: Cytomegalovirus, HIV infection (?) Bacterial: Clostridium difficile, Mycobacterium avium complex Protozoal: Microsporidia (Enterocytozoon bieneusi), Cryptosporidium, Isospora belli
Factitious

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