A. Gastroenteritis

1. Viral: Norwalk agents, adenovirus, Hepatitis A, Rotovirus, poliovirus
2. Bacterial: E. coli, Shigella ssp, Salmonella ssp, C. difficile, Y. enterocolitica, etc.
3. Protozoan: Giardia lambli, Entamoeba histolytica, Toxoplasma gondii, Strongyloides
4. Other: cytomegalovirus (CMV), Mycobacterium avium-intracellulare (MAI)
5. HIV Associated Diarrhea
   1. Bacterial: Campylobacter, C. difficile, MAI, Salmonella, Shigella, Yersinia
   2. Protozoal: cryptosporidium, amoeba, giardia, microsporia (isospora), strongyloides
   3. Viral: adenovirus, CMV, Herpes simplex virus, rotavirus

B. Food Poisoning

1. Staphylococcal ssp - enterotoxin producing strains
2. B. cereus toxins
3. Clostridium botulinum

C. Malabsorption Syndrome

1. Lactose Intolerance
2. Celiac Disease
3. Pancreatic Insufficiency
4. Short Bowel Syndrome
5. Whipple's Disease

D. Inflammatory Bowel Disease

1. Crohn's Disease
2. Ulcerative Colitis
3. Collagenous Colitis
4. Lymphocytic Colitis

E. Secretory Diarrhea

1. Carcinoid Syndrome - seretonin secretion most common (other bioactive amines)
2. WDHHA - watery diarrhea, hypokalemia, hypochlorhydria, acidosis
3. Cholera
4. Zollinger-Ellison Syndrome - gastrinomas (66% sporadic, 33% MEN-1 associated)
5. VIPoma
6. Medullary Carcinoma of THyroid
7. Villous adenoma of rectum
8. Laxative Abuse

F. Miscellaneous

1. Laxative Use / Abuse
2. Irritable Bowel Syndrome (diarrhea variant)
3. Magnesium containing agents
4. Drugs: sulfasalazine and related compounds, cisapride, misoprostal, some antibiotics
5. Early Intestinal Obstruction - distal hypersecretion