Workup and Treatment of Bloody Diarrhea Without Travel History
Primary Recommendation
In immunocompetent patients with bloody diarrhea and no travel history, empiric antibiotics are NOT recommended while awaiting diagnostic results, unless the patient meets specific high-risk criteria: infants <3 months with suspected bacterial etiology, documented fever with bacillary dysentery syndrome (frequent scant bloody stools, fever, abdominal cramps, tenesmus), or signs of sepsis. 1
Diagnostic Workup
Initial Laboratory Testing
Obtain stool studies on a single sample testing for:
- Bacterial culture for Salmonella, Shigella, and Campylobacter 1, 2, 3
- Shiga toxin testing (STEC O157 and other STEC) 1
- Clostridioides difficile testing if antibiotic exposure within the last 3 months 2, 3
- Norovirus testing in outbreak settings 2
Additional testing for severe or persistent cases:
- Complete blood count, creatinine, and electrolytes 3
- Fecal leukocytes or lactoferrin 3
- Blood cultures if sepsis is suspected 1
When to Perform Flexible Colonoscopy
Consider colonoscopy with biopsy when:
- Symptoms persist beyond 14 days to differentiate from inflammatory bowel disease or ischemic colitis 1, 4
- Severe illness with unclear etiology 4
- Immunocompromised patients with persistent symptoms 3
Treatment Algorithm
Rehydration (First-Line for All Patients)
Reduced osmolarity oral rehydration solution (ORS) is the cornerstone of therapy for mild to moderate dehydration in all patients with bloody diarrhea. 1
Empiric Antibiotic Therapy Indications
Initiate empiric antibiotics ONLY in these specific scenarios:
Infants <3 months of age with suspected bacterial etiology 1
- Use third-generation cephalosporin 1
Bacillary dysentery syndrome (presumptive Shigella): documented fever in medical setting + abdominal pain + bloody diarrhea + tenesmus 1
Immunocompromised patients with severe illness and bloody diarrhea 1
- Consider empiric broad-spectrum therapy 1
Signs of sepsis with suspected enteric fever 1
Critical Antibiotic Contraindication
AVOID antibiotics in patients with confirmed or suspected STEC O157 or other STEC producing Shiga toxin 2, as this increases risk of hemolytic uremic syndrome. 1 This is a strong recommendation with moderate-quality evidence.
Pathogen-Specific Management
Once Organism Identified
Modify or discontinue empiric therapy based on identified pathogen and susceptibility results. 1
For Shigella: Azithromycin or fluoroquinolone (based on local resistance patterns) 1
For STEC (Shiga toxin-producing E. coli): Supportive care only; avoid antibiotics 1
For Campylobacter: Azithromycin preferred due to increasing fluoroquinolone resistance globally 5
For Salmonella: Antibiotics generally not indicated unless patient has risk factors for invasive disease (age <3 months, >50 years, immunocompromised, prosthetic implants) 3
Persistent Symptoms (≥14 Days)
Reassess for:
- Noninfectious conditions including inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) 1
- Protozoal infections (consider ova and parasite examination) 3, 6
- Lactose intolerance 1
- Fluid and electrolyte balance, nutritional status 1
Important Caveats
Antimotility Agents
Do NOT use loperamide or other antimotility agents in patients with bloody diarrhea, fever, or suspected invasive bacterial infection. 7, 5 These agents can worsen outcomes in inflammatory diarrhea syndromes.
Contact Management
Asymptomatic contacts should NOT receive empiric treatment but should follow appropriate infection prevention and control measures. 1
Public Health Reporting
Coordinate with local public health authorities for reportable pathogens (Shigella, STEC, Salmonella) to prevent transmission in high-risk settings. 1