Episode 227: Diarrhea

Acute diarrhea in the ED: stool testing, treatment, and a spotlight on Cyclospora.

Hosts:

Neya Vishwanath, MD

Brian Gilberti, MD

https://media.blubrry.com/coreem/content.blubrry.com/coreem/Diarrhea.mp3

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Tags: Gastrointestinal, Gastrointestinal Diseases

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Show Notes

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Framing the Patient

Acute is <2 weeks, persistent is 2–4 weeks, chronic is >30 days. Most acute diarrhea is self-limited and needs only supportive care.

Stool cultures are positive in only 2–6% of unselected patients. Yield rises with >4 stools/day and longer duration.

The ED job is not to name the organism. It is to find volume depletion, rule out the dangerous mimic, and decide who needs testing, antibiotics, or admission.

Don’t-Miss Mimics

Diarrhea is a symptom, not a diagnosis. In anyone who looks sick, gastroenteritis is a diagnosis of exclusion.

Abdominal catastrophes: mesenteric ischemia (pain out of proportion, vascular risk factors), early appendicitis, partial obstruction with overflow stool, diverticulitis.

Systemic disease presenting through the gut: sepsis from another source, DKA, adrenal insufficiency.

Fulminant C. diff or toxic megacolon: distension, fever, tachycardia, peritonitis. The diarrhea may actually stop as the colon dilates.

GI bleeding masquerading as dark diarrhea, and in women of childbearing age, ectopic pregnancy.

History & Exam

Duration, frequency, and appearance. Watery and high-volume suggests small bowel. Small, painful, frequent stools suggest colon.

Volume status: urine output, dark concentrated urine, dry mucous membranes, orthostatic symptoms.

Exposures: recent foods, travel, sick contacts, occupation (animal or sewage contact), recent antibiotics or hospitalization.

Timing after ingestion: <6 hours suggests a preformed toxin (Staph aureus, Bacillus cereus), 8–16 hours suggests Clostridium perfringens, and >16 hours suggests viral or other bacterial causes.

High-risk hosts: pregnancy → Listeria, cirrhosis → Vibrio, hemochromatosis → Yersinia (both siderophilic).

Exam: volume status plus a real abdominal exam. A soft belly does not end the evaluation.

Who Gets Testing

Ask first whether the result will change anything. If the patient is going home on supportive care, a stool study often just generates a callback.

Test when the patient is likely to be admitted or is higher risk: febrile, hypovolemic, elderly (roughly >70), known cardiac disease, immunocompromised, IBD, or pregnant.

Bloodwork is not routine. Send a BMP and CBC for significant hypovolemia, persistent vomiting, bloody stool, or the elderly and comorbid.

Routine cultures cover Salmonella, Campylobacter, Shigella. Ask the lab specifically for Vibrio, Yersinia, Aeromonas, or Listeria.

Know your multiplex GI PCR panel. At many shops it already includes C. diff, so ordering it separately is redundant. One call to your lab settles this.

Bloody stool → send Shiga toxin. Bloody but fecal WBC negative → consider amoebiasis.

Bloody diarrhea plus anemia, thrombocytopenia, or a rising creatinine → think HUS, especially in young children.

Antibiotics or hospitalization within 3 months → C. diff moves up the differential.

Neutropenic patient on active chemotherapy → consider typhlitis (enterocolitis of the cecum).

CT only for peritoneal signs or focal tenderness. It is not part of the routine workup.

Management

Oral rehydration solution is the mainstay for an