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For further information, see CMDT Part 30-08: Acute Infectious Diarrhea

Key Features

Essentials of Diagnosis

  • Acute diarrhea: lasts < 2 weeks

  • Chronic diarrhea: lasts > 2 weeks

  • Mild diarrhea: 3 or fewer stools per day

  • Moderate diarrhea: 4 or more stools per day with local symptoms (abdominal cramps, nausea, tenesmus)

  • Severe diarrhea: 4 or more stools per day with systemic symptoms (fever, chills, dehydration)

General Considerations

  • Acute diarrhea can be caused by a number of different factors, including

    • Emotional stress

    • Food intolerances

    • Inorganic agents (eg, sodium nitrite)

    • Organic substances (eg, mushrooms, shellfish)

    • Medications

    • Infectious agents (including viruses, bacteria, and protozoa)

  • Inflammatory diarrhea

    • Suggests colonic involvement by invasive bacteria, by parasites or by toxin production

    • Common causes include

      • Shigella

      • Salmonella

      • Campylobacter

      • Yersinia

      • Invasive strains of Escherichia coli and other Shiga-toxin–producing strains of E coli (STEC)

      • Entamoeba histolytica

      • Clostridioides difficile

  • Noninflammatory diarrhea

    • Common causes of this syndrome include

      • Viruses (eg, rotavirus, norovirus, astrovirus, enteric adenoviruses), vibriones (Vibrio cholerae, Vibrio parahaemolyticus)

      • Enterotoxin-producing E coli

      • Giardia lamblia

      • Cryptosporidia

      • Agents that can cause food-borne gastroenteritis

      • In developed countries, viruses (particularly norovirus) are an important cause of hospitalizations due to acute gastroenteritis among adults

  • The term "food poisoning" denotes diseases caused by toxins present in consumed foods

  • Epidemiologic features may be helpful in determining etiology:

    • Recent hospitalization or antibiotic use suggests C difficile

    • Recent foreign travel suggests Salmonella, Shigella, Campylobacter, E coli, or V cholerae

    • Undercooked hamburger suggests STEC

    • Outbreak in long-term care facility, school, or cruise ship suggests norovirus (including newly identified strains, eg, GII.4 Sydney)

    • Fried rice consumption is associated with Bacillus cereus toxin

Clinical Findings

  • Inflammatory diarrhea

    • Frequent bloody, small-volume stools

    • Often associated with fever, abdominal cramps, tenesmus, and fecal urgency

  • Noninflammatory diarrhea

    • Generally milder than inflammatory diarrhea

    • Large-volume watery diarrhea, often with nausea, vomiting, and cramps

  • When incubation period of "food poisoning" is short (1–6 hours after consumption),

    • Vomiting is usually a major complaint

    • Fever is usually absent

    • The toxin is usually preformed and can be detected in the food; examples of pathogens with preformed toxins include Staphylococcus aureus or B cereus

  • When the incubation period is longer—between 8 hours and 16 hours

    • Vomiting is less prominent

    • Abdominal cramping is frequent

    • Fever is often absent

    • The organism is present in the food and produces toxin after being ingested; the best example is Clostridium perfringens


  • Inflammatory diarrhea

    • Tests for fecal leukocytes or the neutrophil marker lactoferrin are frequently positive

    • Definitive etiologic diagnosis requires stool culture

  • In cases of "food poisoning," toxin can be detected in food or stool specimens

  • See Table 30–3

Table 30–3.Acute bacterial diarrheas and "food poisoning" (listed in alphabetical order).

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