Why it matters
Gastroenteritis is one of the most common ED presentations worldwide. Most cases are benign and self-limiting, but every rookie needs to remember: behind “just diarrhea” may hide sepsis, severe dehydration, electrolyte derangements, or even surgical pathology. The key is to separate the well from the sick — and to recognize those subtle red flags that can change the outcome.
Etiology & Pathophysiology
- Viral – Norovirus, rotavirus, adenovirus (most common, especially pediatrics).
- Bacterial – Salmonella, Shigella, Campylobacter, E. coli (esp. EHEC), Clostridioides difficile.
- Parasitic – Giardia, Entamoeba histolytica (consider in travel/immigrant history).
Pathophysiology is usually a combination of fluid loss + electrolyte imbalance + systemic inflammation.
Clinical Presentation
- Classic triad: diarrhea, vomiting, abdominal pain/cramping.
- Other common findings: fever, myalgias, malaise.
- Exam focus:
- Hydration status (skin turgor, mucous membranes, cap refill, orthostatic vitals).
- Mental status (esp. elderly and pediatrics).
- Abdominal exam (tenderness, guarding, distension).
Red Flags — Don’t Miss These 🚨
- Severe dehydration: tachycardia, hypotension, lethargy, poor urine output.
- Electrolyte derangements: hypokalemia → arrhythmias; hyponatremia → seizures.
- Bloody diarrhea: think invasive bacterial pathogens, ischemic colitis, IBD flare.
- High fever + toxicity: rule out sepsis.
- Persistent vomiting: metabolic alkalosis, inability to tolerate oral intake.
- Very young, very old, immunocompromised, pregnant – low threshold to admit.
- Abdominal pain out of proportion: mesenteric ischemia, surgical abdomen.
Investigations (when needed)
- Basic labs: CBC, electrolytes, renal function.
- Stool studies: only if severe, bloody, or immunocompromised.
- Imaging: if pain is disproportionate, localized tenderness, or you’re worried about obstruction/ischemia.
- EKG: if severe electrolyte disturbance suspected.
Management in the ED
- Fluids first 💧
- Mild → oral rehydration solutions (ORS).
- Moderate/severe → IV crystalloids (normal saline or LR).
- Electrolyte correction – guided by labs.
- Antiemetics – ondansetron is your friend.
- Antibiotics – not routine!
- Indicated for: severe dysentery, suspected cholera, C. difficile, high-risk patients.
- Symptom relief – paracetamol for fever, loperamide generally avoided in bloody diarrhea/children.
Special Populations
- Pediatrics – higher risk of rapid dehydration; ORS is first-line.
- Elderly – fragile, high risk for AKI and arrhythmias.
- Immunocompromised – lower threshold for admission and stool cultures.
- Pregnancy – avoid fluoroquinolones, metronidazole in first trimester.
Disposition
- Safe for discharge: tolerating PO, stable vitals, mild dehydration, no red flags.
- Admission: severe dehydration, persistent vomiting, inability to hydrate, electrolyte derangements, sepsis suspicion, extremes of age, immunocompromised.
Rookie Pearls 🩺
- Don’t underestimate dehydration in kids — check urine output and cap refill.
- Elderly with “just diarrhea” can tip into shock and AKI very quickly.
- Always ask about recent antibiotic use → think C. difficile.
- Travel history is golden.
- Don’t reflexively prescribe antibiotics — most cases are viral!
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