Acute diarrhea Infectious: viruses (Norwalk, rotavirus, adenovirus), preformed toxin (Staphylococcus aureus, Bacillus cereus, C perfringens), toxin production (enterotoxigenic Escherichia coli, Vibrio cholera), protozoa (Giardia lamblia, Cryptosporidium, Cyclospora, Isospora), invasive or inflammatory (Shigella, Salmonella, Campylobacter, Shiga toxin–producing E coli, C difficile) Noninfectious: drugs, antibiotics, inflammatory bowel disease, laxative abuse, radiation colitis • Chronic diarrhea Osmotic: lactase deficiency, medications (antacids, lactulose, sorbitol, olestra), factitious Secretory: hormonal (carcinoid, VIPoma, medullary thyroid carcinoma, adrenal insufficiency) Inflammatory conditions: inflammatory bowel disease, microscopic colitis, radiation colitis Malabsorption: celiac sprue, small bowel resection, pancreatic insufficiency, bacterial overgrowth, reduced bile salts Motility disorders: irritable bowel syndrome, postsurgical, systemic disease such as diabetes mellitus Chronic infections: giardiasis, amebiasis, strongyloidiasis