What are the recommended antibiotics (Abx) for diverticulitis and the diagnostic study of choice?

Antibiotic Treatment and Diagnostic Study of Choice for Diverticulitis

Diagnostic Study of Choice

CT scan with IV contrast is the recommended first-line imaging modality for diagnosing diverticulitis, with a sensitivity of 98% and specificity of 99%. 1

CT scanning provides detailed visualization of:

• Inflamed colonic segments
• Pericolic inflammation
• Extraluminal air or fluid collections
• Abscess formation
• Perforation

Classification and Treatment Algorithm

Uncomplicated Diverticulitis

For patients with uncomplicated diverticulitis (absence of abscess, strictures, perforation, or fistula):

1. Selective antibiotic use is recommended rather than routine use 1

   • Reserve antibiotics for patients with:
     • Systemic symptoms (fever, chills)
     • Increasing leukocytosis
     • Age >80 years
     • Pregnancy
     • Immunocompromised status
     • Chronic medical conditions (cirrhosis, CKD, heart failure, poorly controlled diabetes)

2. First-line oral antibiotic regimens 1, 2:

   • Amoxicillin-clavulanic acid
   • Cephalexin + metronidazole
   • Ciprofloxacin + metronidazole

3. Management approach:

   • Outpatient treatment for most patients
   • Clear liquid diet initially
   • Pain management (typically acetaminophen)
   • Close monitoring for clinical improvement

Complicated Diverticulitis

For patients with complicated diverticulitis (abscess, perforation, fistula, obstruction):

1. Intravenous broad-spectrum antibiotics covering gram-negative bacilli and anaerobes 1:

   • First-line options:

     • Piperacillin-tazobactam
     • Ertapenem
     • Meropenem or imipenem/cilastatin

   • Combination therapy options:

     • Ceftriaxone + metronidazole
     • Ciprofloxacin + metronidazole
     • Ampicillin + gentamicin + metronidazole

2. Additional interventions based on severity:

   • Percutaneous drainage for abscesses
   • Surgical consultation for:
     • Perforation with diffuse peritonitis
     • Distant intraperitoneal free air
     • Failed medical management

Special Considerations

• Outpatient vs. Inpatient: Outpatient management is not recommended for patients with suspected complicated diverticulitis, recent antibiotic use, unstable comorbid conditions, immunosuppression, or signs of sepsis 1

• Duration of therapy: Typically 7-14 days, though limited evidence exists for optimal duration 3

• Predictors of treatment failure include:

  • Small amounts of distant intraperitoneal gas (57-60% failure rate) 1
  • Symptoms lasting >5 days
  • Vomiting
  • High C-reactive protein levels
  • CT findings of pericolic extraluminal air or fluid collection

Follow-up

• Colonoscopy 6-8 weeks after resolution is recommended to exclude colonic neoplasm if a high-quality examination has not been recently performed 1

• Preventive measures include:

  • High-fiber diet
  • Regular physical activity
  • Smoking cessation
  • Avoidance of NSAIDs, opiates, and corticosteroids

Pitfalls to Avoid

1. Delaying imaging in patients with suspected diverticulitis
2. Using antibiotics routinely for all cases of uncomplicated diverticulitis
3. Failing to recognize signs of complicated disease requiring more aggressive intervention
4. Not providing surgical consultation for patients with evidence of perforation or other complications
5. Missing underlying colorectal cancer by not performing follow-up colonoscopy after resolution

By following this evidence-based approach to diagnosis and treatment, clinicians can effectively manage patients with diverticulitis while minimizing unnecessary antibiotic use and hospitalization.