What antibiotics are used to treat diverticulitis?

Antibiotic Treatment for Diverticulitis

For uncomplicated diverticulitis, antibiotics are no longer routinely recommended, while complicated diverticulitis should be treated with oral amoxicillin-clavulanate or IV regimens such as ceftriaxone plus metronidazole or piperacillin-tazobactam. 1, 2

Classification-Based Treatment Approach

Uncomplicated Diverticulitis

• No routine antibiotics needed for most patients with uncomplicated diverticulitis (absence of abscess, perforation, fistula, or stricture) 1
• Management focuses on:
  • Pain control (acetaminophen preferred over NSAIDs)
  • Clear liquid diet initially, advancing as tolerated
  • Observation for clinical improvement

When to Use Antibiotics in Uncomplicated Diverticulitis

Antibiotics should be used in uncomplicated diverticulitis only if patients have:

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

Antibiotic Regimens

Oral Regimens (for mild-moderate cases)

• First-line: Amoxicillin-clavulanate 1, 2, 3
• Alternative: Cefalexin with metronidazole 1, 2

Intravenous Regimens (for severe or complicated cases)

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

Treatment Duration

• Typically 7-10 days for uncomplicated diverticulitis requiring antibiotics 4
• May be extended if complications develop

Complicated Diverticulitis Management

Small Abscesses (<4-5 cm)

• Antibiotic therapy alone 1

Large Abscesses (≥4-5 cm)

• Percutaneous drainage plus antibiotics 1

Peritonitis

• Immediate surgical intervention with antibiotic therapy
• Fluid resuscitation
• Prompt antibiotic administration 1

Important Clinical Considerations

Evidence on Comparative Effectiveness

• A large cohort study found no difference in clinical outcomes between amoxicillin-clavulanate and metronidazole-with-fluoroquinolone for outpatient diverticulitis treatment 3
• However, C. difficile infection risk was higher with metronidazole-fluoroquinolone combinations in older patients 3

Elderly Patients

• Lower threshold for CT imaging and antibiotic therapy due to atypical presentation
• Only 50% present with typical lower quadrant pain
• Only 17% have fever
• 43% do not have leukocytosis 1

Treatment Failure Warning Signs

• Persistent symptoms beyond 2-3 days
• Worsening clinical condition
• Development of new symptoms (increased pain, fever, inability to tolerate oral intake)
• These warrant further diagnostic investigation and possible change in management 1, 4

Follow-up

• Colonoscopy recommended 4-6 weeks after resolution of complicated diverticulitis to rule out malignancy 1
• Preventive measures include high-fiber diet, regular physical activity, smoking cessation, and avoidance of NSAIDs, opiates, and corticosteroids 1