Diarrhea, Adult

Basics

Description

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

Etiology

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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