Approach to Diarrhea in the ED
Stabilize first. Identify the syndrome. Test only when results change action. Most acute watery diarrhea needs fluids, symptom control, and time, not a broad workup or antibiotics.
Find shock, severe dehydration, sepsis, and the surgical abdomen
- Vitals, mental status, perfusion, urine output, orthostasis when useful
- Dry mucosa, poor skin turgor, tachycardia, hypotension, AKI, major electrolyte loss
- Peritonitis, distention, pain out of proportion, GI bleeding, toxic appearance
- High-risk host: older or frail adult, pregnancy, cirrhosis, ESRD, transplant, chemotherapy, advanced HIV, chronic steroids
Classify before ordering
Watery, uncomplicated
Acute, nonbloody, mild cramps, no high fever, stable host. Viral or toxin-mediated disease is common.
Inflammatory
Blood or mucus, fever, severe focal pain, tenesmus, sepsis. Think invasive bacteria, STEC, IBD, ischemia.
Persistent
≥14 days, weight loss, recurrent symptoms. Think Giardia, Cryptosporidium, Cyclospora, medication, IBD, malabsorption.
Healthcare or antibiotic linked
Recent antibiotics, hospitalization, long-term care, or unexplained persistent diarrhea. Consider C. difficile.
Exposure clues: travel, untreated water, raw shellfish, undercooked meat, sick contacts, shared meals, daycare or facility outbreak, animals, sexual exposure, new medications, laxatives, metformin, magnesium, colchicine, antibiotics, GLP-1 agents.
No routine labs or stool panel for a well adult with uncomplicated watery diarrhea
Bloodwork when clinically useful
- BMP or CMP for significant volume loss, comorbidity, weakness, arrhythmia risk, or expected IV therapy
- CBC, lactate, cultures for sepsis, systemic illness, severe immunocompromise, or suspected enteric fever
- Lipase, LFTs, pregnancy test, TSH, cortisol, or toxicology only when the alternative diagnosis supports it
Send stool testing when higher yield
- Fever, blood or mucus, severe abdominal pain or tenderness, or sepsis
- Severe or prolonged course, immunocompromised host, outbreak concern, or public health implications
- Request Shiga toxin or STEC detection when bloody diarrhea is possible
- C. difficile test only on unformed stool in a compatible syndrome
- Parasite-directed testing for persistent diarrhea or a specific exposure
Multiplex PCR can detect colonization or residual nucleic acid. Interpret the result in the clinical context. Fecal leukocytes and lactoferrin do not establish the cause of acute infectious diarrhea.
Bloody diarrhea plus little or no fever can be STEC.
Send Shiga toxin testing. Avoid empiric antibiotics and antimotility drugs when STEC is plausible because treatment may increase the risk of hemolytic uremic syndrome.
Rehydrate, control symptoms, then use antibiotics selectively
Fluids and symptom control
Empiric antibiotics are the exception
- Do not treat routine acute watery diarrhea without international travel
- Consider for severe febrile dysentery, sepsis with suspected enteric infection, severe traveler’s diarrhea, or severe disease in an immunocompromised host
- Obtain appropriate cultures first when septic or enteric fever is possible
- Use local antibiogram, travel history, and confirmed pathogen to narrow therapy
| Selected adult option | Typical regimen |
|---|---|
| Azithromycin | 1,000 mg once, or 500 mg daily for 3 days. Preferred for dysentery or febrile traveler’s diarrhea. |
| Ciprofloxacin | 750 mg once, or 500 mg twice daily for 3 days when susceptibility and patient factors support use. |
Persistent watery diarrhea should not receive blind antibiotics. Identify and treat the cause. Follow institutional pathways for confirmed or strongly suspected C. difficile.
Discharge the stable, hydrated patient who can drink and follow up
Discharge
- Improved vitals and symptoms after treatment
- Tolerates oral fluids
- No peritonitis, severe electrolyte disorder, AKI requiring monitoring, sepsis, major bleeding, or unsafe social situation
- Clear plan for pending stool results and pathogen-directed treatment
- Soap-and-water hand hygiene. Avoid preparing food for others while symptomatic
Observe, admit, or consult
- Shock, sepsis, severe dehydration, persistent vomiting, altered mental status
- Significant AKI, electrolyte or acid-base disturbance, rhabdomyolysis, or dysrhythmia
- Peritonitis, toxic megacolon, ischemia, obstruction, severe IBD flare, or uncontrolled pain
- High-risk host with systemic illness or inability to maintain hydration
- Concern for HUS: falling platelets, hemolysis, AKI, or neurologic symptoms after diarrheal illness
Return now for: syncope, confusion, minimal urine, inability to drink, worsening or focal abdominal pain, distention, persistent high fever, blood or black stool, dyspnea, or progressive weakness.