Volume, blood, fever, duration (>2 weeks changes the list), restaurant/outbreak, travel, antibiotics, PPI, hospital exposure
Pain out of proportion, AF, vascular disease
Immunosuppression, IBD, pregnancy
Sick contacts, water, undercooked meat
/
Your objective: explain the approach, recognize important warning signs, then test your recall.
Abbreviations explained
- ACS
- Acute coronary syndrome
- OMI
- Occlusion myocardial infarction
- ECG
- Electrocardiogram
- PE
- Pulmonary embolism
- POCUS
- Point-of-care ultrasound
- QTc
- QT interval corrected for heart rate
- LBBB
- Left bundle branch block
- RBBB
- Right bundle branch block
- hs-cTn
- High-sensitivity cardiac troponin
- CTA
- Computed tomography angiography
- ICU
- Intensive care unit
Filter
The jobVolume first; then blood, fever, antibiotics, and the host.
- Volume first.
- Inflammatory (blood, fever, tenesmus) vs non-inflammatory.
- No antibiotics and no loperamide if STEC is possible. Fidaxomicin (or vancomycin) for C. difficile — not metronidazole first-line.
- Pain out of proportion in a vasculopath is CTA, not a stool PCR.
Most ED diarrhea is viral and self-limited.
Resuscitate volume, then sort inflammatory (blood, fever, tenesmus) from non-inflammatory. Do not give antibiotics for suspected STEC (HUS risk). C. difficile is now treated with fidaxomicin preferred or vancomycin — not metronidazole first-line (IDSA/SHEA 2021). Always consider mesenteric ischemia in the older vasculopath with pain out of proportion.
Mesenteric ischemia Critical
Key: Pain out of proportion ± bloody diarrhea in AF or vasculopathy — CTA, not stool studies first.
Toxic megacolon / fulminant C. difficile / IBD Critical
Key: Fever, shock, distension, immunosuppression or recent antibiotics — AXR/CT, surgical consult, oral/NG vancomycin plus IV metronidazole for fulminant CDI; consider rectal vancomycin with ileus (IDSA/SHEA).
STEC / HUS Critical
Key: Bloody diarrhea after undercooked beef or outbreaks, little or no fever — do not give antibiotics or antimotility agents; watch creatinine, hemolysis, platelets.
Cholera / severe secretory dehydration Critical
Key: Rice-water stool, travel; WHO-ORS or IV; antibiotics as an adjunct once volume is restored.
Typhoid / invasive bacterial colitis / amoebiasis Emergent
Key: Fever + blood + travel; cultures; treat per destination and severity. Avoid empiric fluoroquinolones where resistance is high.
Adrenal crisis / thyrotoxicosis / overflow from obstruction Emergent
Key: Not every loose stool is gastroenteritis — look at the whole patient.
Viral gastroenteritis / traveller’s diarrhea Common
Key: ORS, loperamide in non-bloody non-febrile adults; azithromycin for severe traveller’s per CDC.
Tick what your patient has — the banner updates as you go.
Volume status
orthostatics, mucous membranes, cap refill, mental status
Abdomen
peritonitis, distension, masses
Fever; rash (typhoid, HSP); joints and uveitis (IBD, reactive)
PR exam for blood, overflow, mass
Bedside
- Glucose, orthostatics, pregnancy test when appropriate
- POCUS for AAA/free fluid if ischemic or surgical features
Labs
- CBC, creatinine, electrolytes; hemolysis labs if HUS possible (LDH, smear, platelets)
- Stool: C. difficile when antibiotics/healthcare; culture/PCR multiplex per severity and travel; STEC testing if bloody
- Blood cultures if febrile and toxic
Imaging
- CT angiography if mesenteric ischemia is possible
- CT/AXR if obstruction, megacolon, or perforation is possible — skip imaging in straightforward viral illness
Medication safety reminder
Use this as a first-pass prompt; verify all medications, doses, concentrations, contraindications, weight, pregnancy status, and local protocols before administration.
Check indication, allergy, route, renal/hepatic risk, interactions, monitoring, and local formulary.
Discharge
- Non-bloody, well-hydrated after oral challenge, no host red flags — ORS, hygiene, return precautions. Avoid antimotility agents if bloody or febrile.
Admit
- Inability to maintain volume, severe electrolyte derangement, CDI, inflammatory diarrhea needing IV therapy, HUS under observation, high-risk host.
ICU / surgery / IR
- Shock, toxic megacolon, mesenteric ischemia, fulminant CDI, severe HUS.
Use objective reassessment and the local pathway.
Before the next decision · reassess and hand over
Use these learning prompts with the presentation’s pathway. They are not discharge criteria.
- Reassess: compare symptoms, observations and examination with the initial assessment and response to treatment.
- Warning signs for Diarrhea:
- Pain out of proportion, AF, or vasculopathy
- Bloody diarrhea with little fever after ground beef (STEC)
- Recent antibiotics or hospitalization (C. difficile)
- Shock, severe abdominal distension, or immunosuppression
- Fever in a returned traveller
- Anuria, petechiae, or rising creatinine after a diarrheal prodrome (HUS)
- Reconsider: check unresolved findings and alternative explanations, including the pitfalls below.
- Escalate: communicate deterioration, uncertainty or needs beyond the current setting.
- Plan the transition: identify outstanding results, responsibility for follow-up, patient understanding and specific return advice.
Clinical Pearls
- Volume first, then inflammatory vs non-inflammatory, then the host.
- No antibiotics, no loperamide, if STEC is on the list.
- Fidaxomicin (or vancomycin) for CDI — metronidazole only if those are unavailable and disease is non-severe.
- Bloody diarrhea + pain out of proportion = CTA, not a stool PCR first.
Pitfalls
- Antibiotics for STEC increase HUS risk — do not treat empirically “just in case.”
- Metronidazole is no longer first-line for CDI (IDSA/SHEA 2021): fidaxomicin preferred, vancomycin acceptable.
- Loperamide in bloody or febrile diarrhea can precipitate megacolon.
- “Gastroenteritis” in a 75-year-old with AF is mesenteric ischemia until the pain is explained.
- HUS presents after the diarrhea is improving — check the smear and the creatinine.
PRACTICE REFRESHER
Rapid recall
Test your first action and the dangerous diagnoses before revealing the answer.
01 · First move
Before you scroll, what needs to happen first?
Volume first.
02 · Immediate threats
Name at least two diagnoses that cannot wait.
Mesenteric ischemia · Toxic megacolon / fulminant C. difficile / IBD · STEC / HUS
PRIVATE TO THIS DEVICE
Your learning note
Capture a weak point, a teaching pearl, or a question to take to your next shift.
Review schedule starts when marked reviewed
Selected guidance · source check 2026-09-07. These 1 source links support selected teaching points, not a complete review of this topic. Check population, setting and local protocol before applying a recommendation.
- Rosen’s Emergency Medicine, 10th ed. (2023) — diarrhea
- IDSA/SHEA 2021 focused update: C. difficile (fidaxomicin preferred)
- IDSA infectious diarrhea 2017; CDC traveller’s diarrhea; STEC/HUS literature