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  • High fever, frequent bloody stools, severe abdominal pain, dehydration, and no improvement after 3–4 days of initial supportive treatment are worrisome features.

  • Sigmoidoscopy and biopsy are indicated in patients with bloody dysenteric stools and tenesmus lasting more than 3–4 days.

  • Upper endoscopy and biopsy are indicated in patients with persistent diarrhea and evidence of malabsorption.

  • Routine stool cultures aid in identifying Salmonella, Shigella, and Campylobacter but rarely provide useful information if diarrhea develops 2–3 days after hospitalization.

  • Clinical features of shigellosis, salmonellosis, and Campylobacter colitis (diarrhea, tenesmus, fever, abdominal cramps) often overlap.

  • Consider Clostridium difficile infection after both recent and remote (within 3 months) use of antibiotics and if diarrhea develops during hospitalization.

  • Risk factors for severe C difficile infection include age >65, renal failure, immunosuppression, and white blood cell count >20,000/μL.

  • Consider enterohemorrhagic Escherichia coli (E coli O157:H7) in patients with bloody diarrhea, abdominal pain, leukocytosis, and little or no fever, especially if uremia or microangiopathic anemia develops; if suspected, avoid antibiotics.

  • Giardiasis and cryptosporidiosis are best diagnosed using stool immunoassays directed against Giardia and Cryptosporidium antigens which are more sensitive than microscopic stool examination.

  • Up to 10% of patients who have had infectious diarrhea may develop a postinfectious irritable bowel syndrome.


General Considerations

Acute diarrheal diseases remain a major global public health problem, responsible for an estimated 2 million or more deaths annually. Most deaths occur in developing countries and many occur in infants and young children. The majority of acute diarrheal episodes reflect gastrointestinal infections, but medications, food intolerances, or the abrupt onset of chronic disease may be causative (Table 5–1). In the United States, acute diarrheal diseases are a major health and economic problem resulting in between 150 and 300 million total episodes, 900,000 hospitalizations, and approximately 6000–12,000 deaths per year.

Table 5–1.Major causes of acute diarrhea.

Acute diarrheal diseases are second only to respiratory infections as a cause of time lost from work in the United States. As a symptom, diarrhea can be defined as an increase in frequency, volume, and often urgency of the passage of stool and as a decrease in stool consistency. More objectively as a sign, diarrhea is an increase in stool mass to greater than 200 g/24 h, the upper limit of normal stool weight. Acute diarrheal disease is generally defined as having begun within 2 weeks of presentation; diarrhea that persists for between 2 and 4 weeks is ...

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