Acute diarrhea

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  • Almost all true diarrheal emergencies are of noninfectious origin
  • 85% of diarrhea is infectious in etiology
    • Viruses cause vast majority of infectious diarrhea
    • Bacterial causes are responsible for most cases of severe diarrhea
  • Definitions
    • Diarrhea: Increased frequency of defection, usually >3 bowel movements per day
    • Hyperacute: 1-6 hr
    • Acute: less than 3 wks in duration
    • Gastroenteritis: Diarrhea with nausea and/or vomiting
    • Dysentery: Diarrhea with blood/mucus/pus
    • Invasive = Infectious



  1. Possible food poisoning?
    1. Symptoms occur within 6hr
  2. Does it resolve (osmotic) or persist (secretory) w/ fasting?
  3. Are the stools of smaller volume (large intestine) or larger volume (small intestine)
  4. Fever or abdominal pain? (diverticulitis, gastroenteritis, IBD)
  5. Bloody or melenic?
  6. Tenesmus? (shigella)
  7. Malodorous? (giardia)
  8. Recent travel? (Traveler's Diarrhea)
  9. Recent Abx? (C. diff)
  10. HIV/immunocomp/sexual hx
  11. Heat intolerance and anxiety? (thyrotoxicosis)
  12. Paresthesias or reverse temperature sensation? (Ciguatera)

Physical Exam

  1. Thyroid masses
  2. Oral ulcers, erythema nodosum, episcleritis, anal fissure (IBD)
  3. Reactive arthritis (Arthritis, conjunctivitis, urethritis)
    1. Suggests infx w/ salmonella, shigella, campylobacter, or yersinia
  4. Rectal exam for fecal impaction
  5. Guaiac
  6. Abdominal pain out of proportion to exam (mesenteric ischemia)

Toxigenic v. Infectious

Characteristic Toxic Infectious/Invasive
Incubation 2-12h 1-3d
Onset abrupt gradual
Duration <10-24h 1-7days
Fever No Yes
Abdominal Pain Minimal Yes, tenesmus
Systemic No Yes, myalgias, N/V
Physical findings Nontoxic Toxic
Abdominal Tenderness No Yes
Stool Blood, WBCs No Yes


Differential Diagnosis

Acute diarrhea



Watery Diarrhea

Traveler's Diarrhea


Indicated for:

  • Profuse watery diarrhea w/ signs of hypovolemia
  • Severe abdominal pain
  • Fever >38.5 (101.3) (suggests infection w/ invasive bacteria)
  • Symptoms >2-3d
  • Blood or pus in stool (E. coli 0157:H7)
  • Recent hospitalization or abx use
  • Elderly or immunocompromised
  • Systemic illness w/ diarrhea (esp if pregnant (listeria))
  1. Fecal leukocytes
    1. Used to differentiate invasive from noninvasive infectious diarrheas
    2. Sn 50-80%, Sp 83% for presence of bacterial pathogen
    3. If pt has +leukocytes but negative infection consider IBD
  2. Stool culture
    1. Plays minor role in ED evaluation
    2. Yield is only 1.5-5.5%
    3. Consider in pts w/:
      1. Immunosuppression
      2. Severe, inflammatory diarrhea (including bloody diarrhea)
      3. Underlying IBD (need to distinguish between flare and superimposed infection)
  3. O&P
    1. Indicated if parasitic cause is suspected:
      1. Diarrhea >7d
      2. Untreated water
      3. AIDS
      4. Bloody diarrhea w/ few or no fecal leukocytes (intestinal amebiasis)
  4. C. diff toxin
    1. 10% false negative rate
    2. Takes 24hr to run
  5. Chemistry
    1. Warranted in severely dehydrated pts
  6. Abd x-ray
    1. Consider if h/o abdominal sx (r/o obstruction)
  7. CXR
    1. Consider if diarrhea + cough (Legionella)
  8. CT
    1. Consider if suspect mesenteric ischemia


  1. Oral rehydration
    1. Fluids should contain sugar, salt, and water
  2. Probiotics
    1. Lactobacilli and bifidobacterium
    2. 25% decrease in average duration of diarrhea (good evidence)
  3. Food
    1. Eat: BRAT diet (no evidence)
    2. Avoid: Caffeine (incr gastric motility), raw fruit (incr osmotic diarrhea), lactose
  4. Antibiotics
    1. Contraindications:
      1. Suspected or proven EHEC (e.g. O157:H7)
        1. Suspect if bloody diarrhea, abdominal pain, but little or no fever
    2. Indications:
      1. Suspected bacterial diarrhea
        1. Fever
        2. Bloody diarrhea (except for EHEC)
        3. Occult blood or +fecal leukocytes
      2. Moderate to severe travelers' diarrhea (>4 stools/d, fever, blood, or mucus in stool)
      3. >8 stools/d
      4. Volume depletion
      5. >1wk duration
      6. Immunocompromised
      7. Toxic appearance
    3. Ciprofloxacin
      1. First-line choice for empiric therapy
      2. 500mg BID x 3-5d
    4. Azithromycin
      1. Use if fluroquinolone resistance is expected (e.g. Campylobacter from SE Asia)
      2. 500mg QD x3d
  5. Antimotility agents
    1. May mask amount of fluid lost (fluid may pool in the intestine); encourage rehydration
    2. Agents:
      1. Loperamide
        1. Most effective agent
        2. Dose: 4mg; then 2mg after each unformed stool for no more than 2d (max 16mg/d)
        3. Give w/ abx in pts w/ invasive infection
        4. Avoid in pts w/:
          1. Bloody diarrhea
          2. C. diff
          3. High fever
      2. Bismuth subsalicylate
        1. Consider when loperamide is contraindicated (high fever, dysentery)
        2. Dose: 30 mL or 2tab q30 min for 8doses; repeat on day 2
        3. Caution: may cause bismuth encephalopathy in HIV pts
      3. Diphenoxylate and atropine 4mg QID x2d
        1. 2nd line agent (may cause cholinergic side effects


  • Conservatism should be the rule with the young and the elderly

See Also


  1. Marx et al. “Cholera and Gastroenteritis caused by Noncholera Vibrio Species”. Rosen’s Emergency Medicine 8th edition vol 1 pg 1245-1246.