Diarrhea, Adult



Bowel movements characterized as frequent (>3/d), loose, and watery owing to an infectious or toxin exposure


  • Viruses:
    • 50–70% of all cases
  • Invasive bacteria:
    • Campylobacter:
      • Contaminated food or water, wilderness water, birds, and animals
      • Most common bacterial diarrhea
      • Gross or occult blood is found in 60–90%
    • Salmonella:
      • Contaminated water, eggs, poultry, or dairy products
      • Typhoid fever (Salmonella typhi) characterized by unremitting fever, abdominal pain, rose spots, splenomegaly, and bradycardia
    • Shigella:
      • Fecal or oral route
    • Vibrio parahaemolyticus:
      • Raw and undercooked seafood
    • Yersinia:
      • Contaminated food (pork), water, and milk
      • May present as mesenteric adenitis or mimic appendicitis
  • Bacterial toxin:
    • Escherichia coli:
      • Major cause of traveler's diarrhea
      • Ingestion of food or water contaminated by feces
    • Staphylococcus aureus:
      • Most common toxin-related disease
      • Symptoms 1–6 hr after ingesting food
    • Bacillus cereus:
      • Classic source – fried rice left on steam tables
      • Symptoms within 1–36 hr
    • Clostridium difficile:
      • Antibiotic-associated enteritis linked to pseudomembranous colitis
      • Incubation period within 10 d of exposure or initiation of antibiotics
    • Aeromonas hydrophila:
      • Aquatic sources primarily
      • Affects children <3 yr of age
      • Fecal leukocytes absent
    • Cholera:
      • Caused by enterotoxin produced by Vibrio cholerae
      • Profuse watery stools with mucus (classic appearance of rice-water stools)
  • Protozoa:
    • Giardia lamblia:
      • Most common cause of parasite gastroenteritis in North America
      • High-risk groups: Travelers, children in day-care centers, institutionalized people, homosexual men, and campers who drink untreated mountain water
    • Cryptosporidium parvum:
      • Commonly carried in patients with AIDS
    • Entamoeba histolytica (entamebiasis):
      • 5–10% extraintestinal manifestations (hepatic amebic abscess)

Pediatric Considerations
  • Most are viral in origin and self-limited
  • Rotavirus accounts for 50%
  • Shigella: Infections associated with seizures
  • Focus evaluation on state of hydration

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