How should an adult middle‑aged patient with acute uncomplicated diverticulitis (localized left lower quadrant pain, fever less than 38.5 °C, no peritoneal signs, and no imaging evidence of abscess, perforation, fistula, or obstruction) be managed?

Management of Acute Uncomplicated Diverticulitis in Middle-Aged Adults

For an immunocompetent middle-aged patient with acute uncomplicated diverticulitis (localized left lower quadrant pain, fever <38.5°C, no peritoneal signs, and CT-confirmed absence of abscess, perforation, fistula, or obstruction), observation with supportive care alone—without antibiotics—is the recommended first-line approach. 1, 2

Initial Diagnostic Confirmation

Before withholding antibiotics, CT abdomen and pelvis with IV contrast must confirm uncomplicated disease (no abscess, perforation, fistula, obstruction, or bleeding). 1, 3 This imaging achieves 98–99% sensitivity and 99–100% specificity for diverticulitis and is essential because clinical diagnosis alone misclassifies 34–68% of cases. 1, 3

Obtain baseline laboratory studies including complete blood count, C-reactive protein, and basic metabolic panel to assess disease severity and exclude high-risk features. 1, 4

Outpatient Management Without Antibiotics

High-quality randomized controlled trials, including the landmark DIABOLO trial with 528 patients, demonstrate that antibiotics neither accelerate recovery nor prevent complications or recurrence in immunocompetent patients with uncomplicated diverticulitis. 1, 2 In fact, hospital stays are shorter in observation groups (2 vs 3 days). 1

Supportive Care Protocol

• Clear liquid diet during the acute phase (2–3 days), advancing as symptoms improve 1, 4
• Acetaminophen for pain control (avoid NSAIDs, which increase diverticulitis risk) 1, 2
• Adequate oral hydration 1
• Bowel rest initially, then gradual diet advancement 1

Mandatory Follow-Up

Re-evaluation within 7 days is required, or sooner if symptoms worsen. 1 If the patient cannot advance diet after 3–5 days or symptoms persist beyond 5–7 days, obtain repeat CT imaging to assess for complications. 1

Selective Antibiotic Use: High-Risk Features

Reserve antibiotics for patients with ANY of the following high-risk features:

Clinical Indicators

• Persistent fever (>100.4°F) 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, 5

Laboratory Markers

• C-reactive protein >140 mg/L 1, 5
• White blood cell count >15 × 10⁹/L or rising leukocytosis 1, 2

CT Findings

• Fluid collection or abscess 1
• Extensive segment of inflammation 1
• Pericolic extraluminal air 1

Patient Factors

• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 1, 2
• Age >80 years 1, 2
• Pregnancy 1, 2
• Significant comorbidities or frailty (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 1, 2
• ASA physical status III–IV 1, 5

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
• Alternative: Ciprofloxacin 500 mg PO twice daily PLUS Metronidazole 500 mg PO three times daily 1, 2

Inpatient IV Therapy (when hospitalization required)

• Ceftriaxone PLUS Metronidazole 1, 2
• Piperacillin-tazobactam 1, 2
• Transition to oral antibiotics within 48 hours once the patient tolerates oral intake 1

Duration Adjustments

• Immunocompetent patients: 4–7 days total 1, 2
• Immunocompromised patients: 10–14 days total 1, 2

Criteria for Outpatient vs. Inpatient Management

Outpatient Management Appropriate When ALL Present:

• Ability to tolerate oral fluids and medications 1, 6
• No significant comorbidities or frailty 1, 6
• Adequate home and social support 1, 6
• Temperature <100.4°F 1
• Pain controlled with acetaminophen alone (pain score <4/10) 1
• Immunocompetent status 1, 6

Hospitalization 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 1, 2
• Significant comorbidities precluding safe home management 1, 2

Post-Acute Management

Colonoscopy Timing

Schedule colonoscopy 6–8 weeks after symptom resolution for: 1

• First episode of uncomplicated diverticulitis (if no recent high-quality colonoscopy)
• Any complicated episode (7.9% associated cancer risk)
• Patients >50 years needing routine screening
• Presence of alarm features (change in stool caliber, iron-deficiency anemia, rectal bleeding, weight loss)

Recurrence Prevention

Lifestyle modifications proven to reduce recurrence risk: 1

• High-fiber diet (≥22 g/day from fruits, vegetables, whole grains, legumes) combined with low intake of red meat and sweets
• Regular vigorous physical activity
• Maintaining normal BMI (18–25 kg/m²)
• Smoking cessation
• Avoiding nonaspirin NSAIDs when possible

Do NOT restrict nuts, corn, popcorn, or small-seeded fruits—they are not linked to increased diverticulitis risk. 1

Do NOT prescribe mesalamine or rifaximin for prevention—high-certainty evidence shows no benefit but increased adverse events. 1

Special Population: Immunocompromised Patients

Immunocompromised patients require immediate antibiotic therapy (10–14 days), a lower threshold for repeat CT imaging, and early surgical consultation regardless of other factors. 1 This includes patients on corticosteroids (major risk for perforation and death), chemotherapy, or immunosuppression for organ transplantation. 1

Critical Pitfalls to Avoid

• Do NOT prescribe routine antibiotics for uncomplicated diverticulitis without high-risk features—this adds to antimicrobial resistance without clinical benefit 1
• Do NOT assume all patients require hospitalization—most can be safely managed as outpatients with proper follow-up, achieving 35–83% cost savings 1
• Do NOT withhold antibiotics without first confirming uncomplicated disease on CT imaging 1
• Do NOT overlook immunocompromised patients—they need immediate antibiotics regardless of symptom severity 1
• Do NOT fail to arrange mandatory 7-day follow-up—approximately 5% of initially uncomplicated cases develop complications, predominantly within the first 10 days 1, 5