Diarrhea

AdultPediatric
Cannot miss / life threats
Cannot miss / life threats
Diagnostic flow β€” check first
Diagnostic flow β€” check first
  • Vitals + orthostatics FIRST β€” triage volume status / sepsis.
  • Bloody diarrhea β†’ stool culture + PCR; AVOID antimotility (HUS, C. diff, EHEC).
  • Recent abx or hospitalization β†’ C. diff PCR/toxin; check lactate + KUB if severe.
  • Travel / camping / immunocompromised β†’ stool O&P + multiplex PCR.
  • Elderly + vascular disease + pain out of proportion β†’ CT angio for mesenteric ischemia.
  • Acute >38.5Β°C, >6 stools/day, or >7 days β†’ stool studies + consider empiric therapy.
  • Suspected toxic megacolon β†’ KUB (colon >6 cm), surgical consult.
Differential diagnosis β€” checklist
0/21

Check off each diagnosis as you consider it. Tap the name for unique exam, lab/imaging clues, first-line confirmatory test, and management.

Infectious0/6
Inflammatory0/4
Malabsorption / functional0/4
Endocrine / systemic0/4
Drug / toxin0/3
Initial ED workup
Bedside0/4
  • Vitals + orthostatics
  • Abdominal exam (rebound, distension)
  • Rectal exam (blood, melena)
  • Glucose
Labs0/5
  • CBC, BMP, lactate, VBG
  • Stool culture / PCR / C. diff if bloody, prolonged >7 d, immunocompromised, recent abx, or severe
  • Stool O&P if travel / persistent
  • TSH if chronic
  • tTG-IgA if chronic
Imaging0/2
  • Plain film if obstruction / megacolon suspected
  • CT abd/pelvis (with IV contrast) if severe / ischemia / toxic megacolon
Initial management0/6
  • IV fluid resuscitation, replace K/Mg
  • Oral rehydration when tolerated
  • Antiemetic (ondansetron)
  • Empiric antibiotics for severe traveler's / C. diff (PO vancomycin or fidaxomicin)
  • Avoid antimotility agents in bloody / toxin-mediated / C. diff
  • Surgical consult for toxic megacolon / ischemia
ED next steps
ED next steps
  • Vitals + orthostatics; assess for sepsis, dehydration, peritoneal signs; rectal exam (blood, melena).
  • Labs: CBC, BMP, lactate, VBG; stool studies if bloody, >7 days, immunocompromised, recent abx, or severe.
  • C. diff PCR/toxin if recent antibiotics or hospitalization; lactate + abdominal imaging if severe.
  • Plain film or CT abd/pelvis (with IV contrast) if obstruction, toxic megacolon, or ischemia suspected.
  • IV fluid resuscitation (LR), replace K⁺/Mg²⁺; oral rehydration when tolerated; antiemetic.
  • Empiric antibiotics only when indicated (severe traveler's, C. diff: PO vancomycin or fidaxomicin); avoid antimotility agents in bloody / toxin-mediated / C. diff.
  • Disposition: discharge if hemodynamically stable, tolerating PO, normal labs; admit if dehydrated, septic, electrolyte derangement, or surgical concern.
Pearls / pitfalls
Pearls
  • Bloody diarrhea + AKI in a child β†’ think HUS (avoid antibiotics in EHEC).
  • Recent antibiotics or hospitalization + diarrhea β†’ test for C. diff.
  • New 'diarrhea' in elderly with vascular disease and pain out of proportion β†’ mesenteric ischemia.