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For further information, see CMDT Part 15-06: Diarrhea

Key Features

Essentials of Diagnosis

  • Diarrhea is acute in onset with a duration of < 2 weeks

  • Severity ranges from mild and self-limited to severe and life-threatening

General Considerations

  • Most commonly caused by infectious agents, bacterial toxins (Table 30–3), or drugs

  • Recent illnesses in family members suggests infectious diarrhea

  • Community outbreaks (including norovirus and SARS-CoV-2 in nursing homes, schools, cruise ships) suggest a viral etiology or a common food source

  • Among patients with COVID-19 infection, watery diarrhea (usually mild) occurs in 7.7% and it may be the presenting symptom

  • Ingestion of improperly stored or prepared food implicates toxin-secreting or invasive bacteria

  • Exposure to unpurified water suggests Giardia or Cryptosporidium

  • Large Cyclospora outbreaks have been traced to contaminated produce

  • Recent travel abroad suggests "traveler's diarrhea"

  • Antibiotic administration suggests Clostridioides difficile colitis

  • HIV infection or sexually transmitted diseases suggest AIDS-associated diarrhea

  • Proctitis and rectal discharge suggest gonorrhea, syphilis, lymphogranuloma venereum, and herpes simplex

Clinical Findings

Noninflammatory diarrhea

  • Fecal leukocytes and blood are absent

  • Noninflammatory diarrhea may be voluminous with periumbilical cramps, bloating, nausea, or vomiting

  • Usually arises from small bowel due to a toxin-producing bacterium (enterotoxigenic E coli [ETEC], Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Plesiomonas shigelloides) or other agents (viruses, Giardia)

  • Prominent vomiting suggests viral enteritis or Staphylococcus aureus food poisoning

  • May cause dehydration, hypokalemia, and metabolic acidosis

Inflammatory diarrhea

  • Fecal leukocytes are present; blood mixed with stool may also be present (dysentery)

  • Inflammatory diarrhea usually arises from colon, is small volume (< 1 L/day), with left lower quadrant cramps, urgency, and tenesmus

  • Usually caused by invasive organisms (shigellosis, salmonellosis, Campylobacter, or Yersinia infection, amebiasis, cytomegalovirus) or a toxin (C difficile, Aeromonas, Shiga-toxin producing Escherichia coli [STEC, also called enterohemorrhagic E coli)


Laboratory Tests

  • Noninflammatory diarrhea

    • Mild, self-limited, resolving within 5 days in 90%

    • Stool cultures positive in < 3%; therefore, initial symptomatic treatment is given for mild symptoms

  • Diarrhea that requires prompt evaluation

    • Inflammatory diarrhea: fever (> 38.5°C), WBC ≥ 15,000/mcL (15 × 109/L), bloody diarrhea, or severe abdominal pain

    • Passage of six or more unformed stools in 24 hours

    • Profuse watery diarrhea and dehydration

    • Frail older patients

    • Immunocompromised patients (AIDS, posttransplantation)

    • Exposure to antibiotics

    • Hospital-acquired diarrhea (onset following at least 3 days of hospitalization)

    • Systemic illness

  • Three stool examinations for ova and parasites should be obtained to look for amebiasis in those whose diarrhea persists > 10 days, in those who engage in oral-anal sexual practices, and in those with recent travel to amebiasis endemic areas

  • Stool C difficile toxin assay if recent history of antibiotic exposure or hospitalization

  • Rectal swab cultures for Chlamydia...

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