1. In all patients with diarrhea,
    1. Determine hydration status,
    2. Treat dehydration appropriately.
  2. In patients with acute diarrhea, use history to establish the possible etiology (e.g., infectious contacts, travel, recent antibiotic or other medication use, common eating place for multiple ill patients).
  3. In patients with acute diarrhea who have had recent hospitalization or recent antibiotic use, look for clostridium difficile.
  4. In patients with acute diarrhea, counsel about the timing of return to work/school (re: the likelihood of infectivity).
  5. Pursue investigation, in a timely manner, of elderly with unexplained diarrhea, as they are more likely to have pathology.
  6. In a young person with chronic or recurrent diarrhea, with no red flag symptoms or signs, use established clinical criteria to make a positive diagnosis of irritable bowel syndrome (do not overinvestigate).
  7. In patients with chronic or recurrent diarrhea, look for both gastro-intestinal and non-gastro-intestinal symptoms and signs suggestive of specific diseases (e.g., inflammatory bowel disease, malabsorption syndromes, and compromised immune system).

See irritable bowel syndrome, inflammatory bowel disease.

General Overview

  • Acute: 2-14 days of looser and more frequent stools (>3 stools/day or >200g stool/d)
    • Parasitic - Giardia, cryptosporidia, cyclospora, isospora, amoebiasis
    • Bacteria - Campylobacter, salmonella, shigella, listeria, C diff, S Aureus, Clostridium perfrigens
      • Symptoms suggestive of invasive bacterial diarrhea include fever, tenesmus, gross bloody stool
    • Viral - Hep A, rotavirus, norovirus
    • Travel - ETEC, norovirus, shigella, salmonella, campylobacter, giardia
    • Daycare - Campylobacter, cryptosporidia, parvum
    • Hospital - C Diff, norovirus, rotavirus (children)
  • Chronic: >4 weeks
    • Function - IBS (10-20%), overflow constipation, incontinence
    • Osmotic - Lactose, sugars (sorbitol, mannitol), laxatives
    • Inflammatory - IBD, microscopic/collagenous colitis
    • Metabolic - Addison's, hyperthyroid, uremia, cystic fibrosis
    • Malabsorption - Pancreatitis, celiac, short bowel syndrome, bacterial overgrowth
    • Neoplastic - Colorectal cancer, carcinoid, gastrinoma, medullary thyroid
    • Iatrogenic - Drugs, alcohol, caffeine, surgery, radiation, laxatives
  • Secretory: Continues despite fasting
  • Osmotic: Decreases with fasting (malabsorption, drugs)
  • Large Bowel: Small volume, frequent, pus, blood
  • Small Bowel: Large volume, infrequent, watery


  • Travel
  • Immunocompromised
  • Food outbreaks
  • Antibiotics
  • Family History
  • Laxatives

Red Flags

  • Age >50 (think of acute mesenteric ischemia, obstruction, diverticulitis, malignancy)
  • Immunocompromised (HIV, steroid)
  • Inflammatory features (fever, bloody, mucoid stool)
  • N/V, fever, arthritis, skin rash, anorexia
  • Night sweats, weight loss
  • Nocturnal (pathologic)
  • Recent antibiotics (C-diff)


  • Diarrhea onset, duration, severity, frequency, quality (watery, bloody, mucus, purulent, bilious)
  • Signs of dehydration (decreased urine output, altered mental status)
  • Vomiting (viral or toxin)
  • Fever, tenesmus, bloody (invasive bacterial)
  • Food/Travel
  • Pregnant (12x risk of listeriosis - cold meats, soft cheeses, raw milk)
  • Recent sick contacts, antibiotics, medications
  • Immunosupression
  • Exposures (daycare, fecal-oral sexual contact, hospital admission)

Physical Exam

  • Vitals, orthostatic hypotension, temperature
  • Signs of dehydration (decreased urine output, skin turgor)
  • Abdominal exam
  • Rectal exam (assess stool)


  • Usually not indicated unless severe illness or red flags
  • Consider
    • CBC, CRP, TSH, Celiac (IgA, anti-TTG)
    • FOBT or FIT
    • Stool leukocytes/lactoferrin/calprotectin (r/o IBD)
    • Stool cultures if leukocytes positive or risk factor/red flag (eg. symptomatic bloody diarrhea)
    • C-diff toxins A/B done if unexplained diarrhea after 3d of hospitalization or high risk (eg. antibiotic use)
    • Ova and parasites if high-risk (travel to high-risk area, infants in day care, immunosuppresssed, MSM, waterborne outbreak, bloody diarrhea with few fecal leukocytes)
      • If available, consider Giardia antigen test or PCR
    • C-scope if altered bowel habit +/- rectal bleeding


  • Rehydration (oral if possible)
    • Consider reduced oral rehydration solution (ORS): water with salt and glucose
  • Early refeeding
    • No clear evidence for BRAT diet (banana, rice, applesauce, toast) and avoidance of dairy
  • Loperamide/simethicone in non-bloody stool and afebrile
  • Consider empiric antibiotics in severe symptomatic bloody diarrhea or immunocompromised
    • Fluoroquinolone or Azithromycin (if resistance, eg. from South East Asia)
    • Antibiotics effective in shigella, campylobacter, C diff, traveler's diarrhea, protozoal
    • Avoid use in toxin (bloody, history of eating seed sprouts, rare beef, outbreak) risk Hemolytic uremic syndrome


  • Hygiene (handwashing, diaper changing, water purification), safe food preparation, clean water
  • Vaccine (rotavirus, typhoid fever, cholera)
  • No clear evidence for probiotics, zinc supplementation
  • Return to school ≥48h last diarrhea/vomiting (NICE)