What are the first line antibiotics for diverticulitis?

First-Line Antibiotics for Diverticulitis

For uncomplicated diverticulitis, antibiotics are generally not recommended as first-line treatment, while for complicated diverticulitis, the first-line antibiotic regimens include oral amoxicillin-clavulanate or cefalexin with metronidazole for outpatient treatment, and IV ceftriaxone plus metronidazole, piperacillin-tazobactam, or ampicillin/sulbactam for inpatient treatment. 1

Antibiotic Recommendations Based on Disease Classification

Uncomplicated Diverticulitis

• No antibiotics recommended for most patients with uncomplicated diverticulitis
• Management focuses on:
  • Pain control (acetaminophen preferred over NSAIDs)
  • Clear liquid diet initially, advancing as tolerated 1

Complicated Diverticulitis

• Oral regimens (for outpatient management):

  • Amoxicillin-clavulanate OR
  • Cefalexin with metronidazole 1, 2

• IV regimens (for inpatient management):

  • Ceftriaxone plus metronidazole OR
  • Piperacillin-tazobactam OR
  • Ampicillin/sulbactam 1, 2

When to Use Antibiotics in Uncomplicated Diverticulitis

Despite the general recommendation against routine antibiotic use in uncomplicated diverticulitis, antibiotics should be considered in patients with:

• Systemic symptoms (persistent fever, chills)
• Increasing leukocytosis
• Age >80 years
• Pregnancy
• Immunocompromised status (receiving chemotherapy, high-dose steroids, or post-organ transplant)
• Significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 1, 2

Management Algorithm

1. Diagnosis confirmation: CT scan with IV contrast (98% sensitivity, 99% specificity) 1

2. Disease classification:

   • Uncomplicated: No abscess, phlegmon, fistula, obstruction, bleeding, or perforation
   • Complicated: Presence of any of the above complications

3. Treatment approach:

   • Uncomplicated diverticulitis:

     • Conservative management without antibiotics for most patients
     • Consider antibiotics only for high-risk patients (as listed above)

   • Complicated diverticulitis:

     • Always treat with antibiotics
     • Small abscesses (<4-5 cm): Antibiotics alone
     • Large abscesses (≥4-5 cm): Percutaneous drainage plus antibiotics
     • Peritonitis: Surgical intervention with antibiotic therapy 1

Special Considerations

• Elderly patients (>65 years) have atypical presentations and higher risk of complications, warranting a lower threshold for CT imaging and antibiotic therapy 1

• Outpatient vs. inpatient treatment: Recent evidence shows that oral antibiotics are as effective as IV antibiotics for outpatient management of uncomplicated diverticulitis 3

• Duration of therapy: While optimal duration is not well-established in the literature, 7-10 days is commonly recommended 2, 4

• Prevention strategies: High-fiber diet, regular physical activity, smoking cessation, and avoidance of regular NSAID, opiate, and corticosteroid use 1

Common Pitfalls to Avoid

1. Overuse of antibiotics in uncomplicated diverticulitis when not indicated

2. Inadequate coverage of both gram-negative and anaerobic pathogens when antibiotics are indicated

3. Failure to recognize when a patient with uncomplicated diverticulitis needs antibiotics due to risk factors

4. Delayed surgical consultation in cases of complicated diverticulitis with peritonitis or large abscesses

5. Inadequate follow-up: Colonoscopy is recommended 4-6 weeks after resolution of complicated diverticulitis to rule out malignancy 1