Diagnostic Approach and Initial Treatment for Acute Infective Colitis
The recommended diagnostic approach for acute infective colitis includes stool culture, flexible sigmoidoscopy with biopsy, and CT imaging with IV contrast, followed by targeted antimicrobial therapy based on identified pathogens or empiric treatment with azithromycin for febrile dysenteric diarrhea when awaiting results. 1
Initial Diagnostic Evaluation
Clinical Assessment
- Evaluate for key symptoms:
- Diarrhea (bloody or non-bloody)
- Fever
- Abdominal pain
- Rectal bleeding
- Assess for risk factors:
- Recent antibiotic exposure (suggests C. difficile)
- Recent travel history
- Immunocompromised status
- Exposure to contaminated food/water
Laboratory Testing
- Complete blood count (CBC) to assess for leukocytosis
- Inflammatory markers (CRP, ESR)
- Stool studies:
- Multiplex PCR testing for bacterial, viral, and parasitic pathogens (preferred first-line test) 2
- Stool culture for bacterial pathogens (Shigella, Salmonella, Campylobacter)
- C. difficile toxin assay (especially with recent antibiotic exposure)
- Stool for inflammatory markers (leukocytes, lactoferrin, calprotectin) 1
Imaging and Endoscopy
Flexible sigmoidoscopy with biopsy is the gold standard for diagnosis (diagnostic precision >90%) 3
- Particularly valuable when infectious colitis is suspected
- Can identify characteristic findings such as segmental involvement, petechial hemorrhages, and longitudinal ulcers
- Allows for direct visualization and tissue sampling
CT scan with IV contrast (sensitivity 53-85%, specificity 75-78%) 3
- Helpful to assess extent of disease and exclude complications
- Can identify bowel wall thickening, mucosal enhancement, and pericolonic fat stranding
Initial Treatment Approach
Conservative Management
- Fluid and electrolyte replacement
- IV fluid resuscitation for dehydration
- Potassium supplementation (at least 60 mmol/day) to prevent toxic dilatation 4
- Bowel rest as appropriate for symptom severity
Antimicrobial Therapy
Targeted therapy based on identified pathogen:
- For C. difficile: Oral metronidazole 250 mg four times daily for 10 days (first-line) or oral vancomycin 125-500 mg four times daily for 10 days (for severe cases or metronidazole failures) 5
- For bacterial pathogens: Pathogen-specific antibiotics based on susceptibility testing
Empiric therapy when awaiting results:
- For febrile dysenteric diarrhea: Single dose azithromycin 1000 mg 1
- Broad-spectrum antibiotics for severe cases with systemic symptoms
Special Considerations
For severe colitis:
- Daily physical examination and vital sign monitoring
- Laboratory monitoring
- Consider early surgical consultation if no improvement within 48-72 hours 3
For cytomegalovirus (CMV) colitis:
Monitoring and Follow-up
- Assess response to treatment within 48-72 hours
- Consider surgical intervention for:
- Clinical deterioration despite medical management
- Peritoneal signs
- Free perforation
- Life-threatening hemorrhage 3
Differential Diagnosis
- Inflammatory bowel disease (ulcerative colitis, Crohn's disease)
- Ischemic colitis
- Drug-induced colitis
- Radiation colitis
- Neutropenic enterocolitis 3
Pitfalls to Avoid
- Delaying diagnosis and treatment in severe cases
- Failing to test for C. difficile in patients with recent antibiotic exposure
- Overuse of antimotility agents in infectious colitis with fever or bloody diarrhea
- Missing CMV colitis in immunocompromised or steroid-resistant patients
- Delaying surgical consultation in deteriorating patients
By following this systematic approach to diagnosis and treatment, clinicians can effectively manage acute infective colitis while minimizing complications and improving patient outcomes.