When are antibiotics necessary in diverticulitis?

Antibiotic Use in Diverticulitis Management

Antibiotics should be reserved for complicated diverticulitis or uncomplicated diverticulitis with specific risk factors, while most cases of uncomplicated diverticulitis can be safely managed without antibiotics. 1, 2

Uncomplicated Diverticulitis (No Antibiotics Needed)

Uncomplicated diverticulitis (approximately 85% of cases) can be managed conservatively without antibiotics through:

• Observation with pain management (typically acetaminophen)
• Dietary modification with clear liquids initially
• Outpatient management for patients who can tolerate oral intake 1, 2

Multiple studies have demonstrated that antibiotics do not improve outcomes in uncomplicated diverticulitis, including:

• No significant difference in complication rates
• No reduction in recurrence rates
• No difference in need for surgical intervention
• Similar length of hospital stay 3, 4, 5

When Antibiotics ARE Necessary

1. Complicated Diverticulitis

Antibiotics are always indicated for complicated diverticulitis, defined by:

• Abscess formation
• Perforation
• Fistula formation
• Stricture development
• Peritonitis 1, 2

For complicated cases:

• Intravenous antibiotics (ceftriaxone plus metronidazole or piperacillin-tazobactam)
• Small abscesses: 7 days of antibiotic therapy
• Large abscesses: percutaneous drainage plus 4 days of antibiotics 1

2. Uncomplicated Diverticulitis with Risk Factors

Antibiotics should be administered in uncomplicated diverticulitis when patients have:

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

Antibiotic Selection and Duration

When antibiotics are indicated:

• Outpatient treatment (oral): Amoxicillin/clavulanic acid or cefalexin with metronidazole
• Inpatient treatment (IV): Ceftriaxone plus metronidazole, ampicillin/sulbactam, or piperacillin-tazobactam
• Duration: 4-7 days (4 days for immunocompetent patients with adequate source control; up to 7 days for immunocompromised or critically ill patients) 1, 2

Clinical Pearls and Pitfalls

Pearls:

• CT scan with IV contrast is the preferred diagnostic test (sensitivity 98%, specificity 99%) 1
• Patients with uncomplicated diverticulitis who can take fluids orally may be managed as outpatients 1
• Only 2.7% of patients initially managed without antibiotics later require them 3

Pitfalls to Avoid:

• Overuse of antibiotics in uncomplicated diverticulitis without risk factors
• Failure to recognize predictors of progression to complicated disease:
  • Symptoms lasting >5 days
  • Initial pain score >7
  • Vomiting
  • Systemic comorbidity
  • Elevated white blood cell count
  • High C-reactive protein levels
  • CT findings of pericolic extraluminal air or fluid collection 1

Follow-up

• Patients with complicated diverticulitis should undergo colonoscopy 4-6 weeks after resolution to rule out malignancy
• Routine colonoscopy is not required after uncomplicated diverticulitis 1