Management of Acute Diverticulitis
For hemodynamically stable adults without significant comorbidities and uncomplicated diverticulitis, observation with supportive care alone—without routine antibiotics—is the recommended first-line approach. 1, 2
Initial Diagnostic Evaluation
Obtain CT abdomen-pelvis with IV contrast to confirm the diagnosis, classify disease severity, and exclude complications. CT provides 98–99% sensitivity and 99–100% specificity for acute diverticulitis 3, 4. Clinical examination alone misdiagnoses 34–68% of cases 4.
Order complete blood count and C-reactive protein to assess inflammatory burden and guide risk stratification 3.
Disease Classification
Uncomplicated Diverticulitis
- CT findings: Diverticula, bowel wall thickening, increased pericolic fat density—without abscess, perforation, fistula, obstruction, or free air 3, 1
- Represents approximately 88% of acute diverticulitis cases 4
Complicated Diverticulitis
- CT findings: Abscess formation, extraluminal gas, perforation, fistula, obstruction, or distant free fluid 3, 1
- Requires immediate antibiotic therapy and possible intervention 1, 2
Treatment Algorithm for Uncomplicated Diverticulitis
Step 1: Determine Outpatient vs. Inpatient Management
Outpatient management is appropriate when ALL of the following criteria are met:
- Ability to tolerate oral fluids and medications 1, 2
- Temperature <100.4°F (38°C) 1
- Pain controlled with acetaminophen alone (pain score <4/10) 1
- No significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 1, 2
- Adequate home and social support 1, 2
- Immunocompetent status 1, 2
Hospitalization is required for:
- Complicated diverticulitis on CT 1, 2
- Inability to tolerate oral intake 1, 2
- Signs of systemic inflammatory response or sepsis 1, 2
- Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 1, 2
- Significant comorbidities or frailty 1, 2
Step 2: Decide on Antibiotic Use
For immunocompetent patients with uncomplicated diverticulitis, withhold antibiotics and use observation with supportive care. Multiple high-quality randomized trials (including the DIABOLO trial with 528 patients) demonstrate that antibiotics do not accelerate recovery, prevent complications, or reduce recurrence 1, 2, 5.
Reserve antibiotics ONLY for patients with ANY of these high-risk features:
Clinical indicators:
- Persistent fever or chills despite supportive care 1, 2
- Refractory symptoms or vomiting 1, 2
- Inability to maintain oral hydration 1, 2
- Symptom duration >5 days before presentation 1, 2
Laboratory markers:
CT findings:
- Fluid collection or abscess 1, 2
- Longer segment of colonic inflammation 1, 2
- Pericolic extraluminal air 1, 2
Patient factors:
- Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 1, 2
- Age >80 years 1, 2
- Pregnancy 1, 2
- ASA physical status III–IV 1, 2
- Significant comorbidities or frailty 1, 2
Antibiotic Regimens (When Indicated)
Outpatient Oral Therapy (4–7 days for immunocompetent patients)
First-line: Amoxicillin-clavulanate 875/125 mg PO twice daily 1, 2, 4
Alternative: Ciprofloxacin 500 mg PO twice daily PLUS metronidazole 500 mg PO three times daily 1, 2, 4
Inpatient IV Therapy (transition to oral within 48 hours when tolerated)
Standard regimens:
- Ceftriaxone PLUS metronidazole 1, 2, 4
- Piperacillin-tazobactam 1, 2, 4
- Amoxicillin-clavulanate 1.2 g IV every 6 hours 1, 4
Duration:
- Immunocompetent patients: 4–7 days total 1, 2, 4
- Immunocompromised patients: 10–14 days total 1, 2, 4
Supportive Care (All Patients)
Dietary management:
- Clear liquid diet during acute phase (2–3 days) 1, 2
- Advance diet as symptoms improve 1, 2
- If unable to advance diet after 3–5 days, arrange immediate follow-up 1
Pain control:
Hydration:
Management of Complicated Diverticulitis
Small Abscess (<4–5 cm)
IV antibiotics alone for 7 days with gram-negative and anaerobic coverage 1, 2, 4
Large Abscess (≥4–5 cm)
Percutaneous CT-guided drainage PLUS IV antibiotics 1, 2, 4
- Continue antibiotics for 4 days after adequate source control in immunocompetent patients 1, 2, 4
- Cultures from drainage guide antibiotic selection 1, 4
Generalized Peritonitis or Sepsis
Emergent surgical consultation for source control (Hartmann procedure or primary resection with anastomosis) PLUS broad-spectrum IV antibiotics 1, 2, 4
Follow-Up and Monitoring
Mandatory re-evaluation within 7 days of initial presentation (or sooner if symptoms worsen) 1, 2, 4
Colonoscopy 6–8 weeks after symptom resolution for:
- First episode of uncomplicated diverticulitis (if no recent high-quality colonoscopy) 1, 2
- Any complicated diverticulitis (7.9% associated cancer risk) 1, 2
- Patients >50 years requiring routine screening 1, 2
- Alarm features (change in stool caliber, iron-deficiency anemia, rectal bleeding, weight loss) 1, 2
Prevention of Recurrence
Lifestyle modifications:
- High-fiber diet (≥22 g/day from fruits, vegetables, whole grains, legumes) 1, 2
- Regular vigorous physical activity 1, 2
- Achieve or maintain normal BMI (18–25 kg/m²) 1, 2
- Smoking cessation 1, 2
- Avoid nonaspirin NSAIDs when possible 1, 2
Do NOT restrict nuts, corn, popcorn, or small-seeded fruits—they are not associated with increased diverticulitis risk 1, 2
Do NOT prescribe mesalamine or rifaximin for prevention—high-certainty evidence shows no benefit but increased adverse events 1, 2
Special Populations
Immunocompromised Patients
Require immediate antibiotic therapy (10–14 days), lower threshold for CT imaging, and early surgical consultation regardless of other factors 1, 2, 4. Corticosteroid use specifically increases risk of perforation and death 1, 2.
Elderly Patients (>65 years)
Lower threshold for antibiotic treatment and closer monitoring even when other outpatient criteria are met 1, 4. Require antibiotic therapy even for localized complicated diverticulitis 4.
Critical Pitfalls to Avoid
Do NOT prescribe routine antibiotics for uncomplicated diverticulitis without high-risk features—this contributes to antibiotic resistance without clinical benefit 1, 2, 5.
Do NOT assume all patients require hospitalization—outpatient management achieves 35–83% cost savings with only 4.3% failure rate requiring later admission 1, 2.
Do NOT apply the "no antibiotics" approach to complicated diverticulitis (Hinchey 1b or higher with abscess)—the evidence specifically excluded these patients 1, 2.
Do NOT withhold antibiotics without first confirming uncomplicated disease on CT imaging—all studies supporting observation required imaging to rule out complications 1, 4.
Do NOT overlook immunocompromised patients—they need immediate antibiotics (10–14 days) and lower threshold for repeat imaging and surgical consultation 1, 2.
Do NOT stop antibiotics early even if symptoms improve—complete the full prescribed course 1, 2.