How should diverticulitis be managed, distinguishing uncomplicated from complicated disease, including outpatient versus inpatient criteria (fever >38.5 °C, leukocytosis >12 × 10⁹/L, peritoneal signs), appropriate antibiotic regimens, and indications for drainage or surgery?

Management of Diverticulitis

Initial Assessment and Classification

For patients with suspected diverticulitis, obtain a contrast-enhanced CT scan of the abdomen and pelvis to confirm the diagnosis and distinguish uncomplicated from complicated disease—this imaging has 98-99% sensitivity and 99-100% specificity. 1, 2 Clinical diagnosis alone is unreliable, with misdiagnosis rates of 34-68%, and CT imaging reduces unnecessary hospital admissions by over 50%. 3

Uncomplicated diverticulitis is defined as localized colonic inflammation with diverticula, wall thickening, and pericolic fat stranding, without abscess, perforation, fistula, obstruction, or bleeding. 1, 3 Complicated diverticulitis involves any of these features: abscess formation, perforation, fistula, obstruction, or bleeding. 1, 3

Obtain a complete blood count and C-reactive protein to assess disease severity and guide risk stratification. 3, 2

---

Outpatient vs. Inpatient Criteria

Outpatient Management is Appropriate When ALL of the Following Are Met:

• Ability to tolerate oral fluids and medications 4, 3
• Temperature <38.5°C (100.4°F) 4, 3
• Pain score <4/10 on visual analog scale, controlled with acetaminophen alone 4, 3
• No significant comorbidities or frailty (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 4, 3
• Adequate home and social support for monitoring 4, 3
• Immunocompetent status 4, 3
• No signs of systemic inflammatory response or sepsis 4, 3

Outpatient management achieves 35-83% cost savings per episode compared to hospitalization, with only a 4.3% failure rate requiring subsequent admission. 4, 3

Hospitalization is Indicated For:

• Complicated diverticulitis on CT (abscess, perforation, obstruction, fistula) 4, 3
• Inability to tolerate oral intake 4, 3
• Fever >38.5°C or signs of sepsis 4, 3
• Leukocytosis >12-15 × 10⁹/L or rising white blood cell count 4, 3, 5
• Peritoneal signs on examination 1, 3
• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 4, 3, 2
• Significant comorbidities or frailty 4, 3
• Age >80 years 4, 3, 2
• Pregnancy 4, 3, 2

---

Antibiotic Management for Uncomplicated Diverticulitis

When to WITHHOLD Antibiotics (Observation Only):

For immunocompetent patients with uncomplicated diverticulitis confirmed by CT, observation with supportive care alone is the first-line approach—antibiotics do NOT accelerate recovery, prevent complications, or reduce recurrence. 4, 3 This recommendation is based on high-quality evidence from the DIABOLO trial (528 patients) and multiple other randomized controlled trials. 4, 3

Supportive care includes:

• Clear liquid diet during the acute phase (2-3 days), advancing as tolerated 4, 3
• Adequate oral hydration 4, 3
• Acetaminophen for pain control (avoid NSAIDs) 4, 3, 2

When to START Antibiotics Immediately:

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

Clinical indicators:

• Persistent fever >38.5°C or chills despite supportive care 4, 3
• Refractory symptoms or persistent vomiting 4, 3
• Inability to maintain oral hydration 4, 3
• Symptoms lasting >5 days before presentation 4, 3

Laboratory indicators:

• C-reactive protein >140 mg/L 4, 3, 5
• White blood cell count >15 × 10⁹/L or rising leukocytosis 4, 3

CT imaging findings:

• Fluid collection or abscess 4, 3
• Pericolic extraluminal air 4, 3
• Longer segment of colonic inflammation 4, 3

Patient factors:

• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 4, 3, 2
• Age >80 years 4, 3, 2
• Pregnancy 4, 3, 2
• ASA physical status III or IV 4, 3
• Significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 4, 3, 2

---

Antibiotic Regimens

Outpatient Oral Therapy (4-7 days for immunocompetent patients):

First-line options:

• Amoxicillin-clavulanate 875/125 mg PO twice daily (validated in the DIABOLO trial) 4, 3, 2
• Ciprofloxacin 500 mg PO twice daily PLUS metronidazole 500 mg PO three times daily 4, 3, 2

Inpatient IV Therapy (transition to oral within 48 hours when tolerated):

IV regimens:

• Ceftriaxone PLUS metronidazole 4, 3, 2
• Piperacillin-tazobactam 4, 3, 2
• Amoxicillin-clavulanate 1.2 g IV every 6 hours 4

Transition to oral antibiotics as soon as the patient tolerates oral intake to facilitate earlier discharge—hospital stays are actually shorter (2 vs 3 days) in observation groups compared to antibiotic-treated patients. 4, 3

Duration of Therapy:

• Immunocompetent patients: 4-7 days total 4, 3, 2
• Immunocompromised patients: 10-14 days total 4, 3
• After percutaneous drainage of abscess: 4 days post-source control in immunocompetent patients 4, 3

---

Management of Complicated Diverticulitis

Small Abscess (<4-5 cm):

Treat with IV antibiotics alone for 7 days. 4, 3, 6, 7 Percutaneous drainage is not required for abscesses smaller than 4-5 cm. 4, 3

Large Abscess (≥4-5 cm):

Perform CT-guided percutaneous drainage PLUS IV antibiotics. 1, 4, 3, 6, 7 After successful source control, continue antibiotics for an additional 4 days in immunocompetent patients. 4, 3 Obtain cultures from drainage to guide antibiotic selection. 3

Generalized Peritonitis or Sepsis:

Obtain emergent surgical consultation for source control surgery (Hartmann procedure or primary resection with anastomosis) AND start broad-spectrum IV antibiotics immediately. 1, 4, 3, 2 Laparoscopic peritoneal lavage should NOT be considered the treatment of choice. 3

---

Follow-Up and Monitoring

All outpatients must be re-evaluated within 7 days of diagnosis, or sooner if clinical status worsens. 4, 3 If symptoms persist after 5-7 days of antibiotic therapy, perform urgent repeat CT imaging to assess for complications requiring drainage or surgery. 4, 3

Colonoscopy should be performed 6-8 weeks after symptom resolution for patients with complicated diverticulitis (7.9% risk of colon cancer), first episode of uncomplicated diverticulitis in patients >50 years requiring routine screening, or when alarm features are present (change in stool caliber, iron-deficiency anemia, rectal bleeding, weight loss). 3 The risk of colorectal cancer in uncomplicated diverticulitis is only 1.16%, so colonoscopy is not routinely required if recent high-quality colonoscopy was performed. 3

---

Prevention of Recurrence

Lifestyle modifications to reduce recurrence risk:

• High-fiber diet (≥22 g/day from fruits, vegetables, whole grains, legumes) combined with low intake of red meat and sweets 4, 3
• Regular vigorous physical activity 4, 3
• Achieving or maintaining normal BMI (18-25 kg/m²) 4, 3
• Smoking cessation 4, 3
• Avoiding nonaspirin NSAIDs when possible (aspirin use does not need to be routinely avoided) 4, 3

Do NOT restrict consumption of nuts, corn, popcorn, or small-seeded fruits—these are not associated with increased risk of diverticulitis. 4, 3

Do NOT prescribe mesalamine or rifaximin for prevention of recurrent diverticulitis—high-certainty evidence shows no benefit but increased adverse events. 4, 3

---

Surgical Considerations for Recurrent Diverticulitis

The traditional "two-episode rule" for elective surgery is no longer accepted. 4, 3 The decision for elective resection should be based on quality of life impact, frequency of recurrence (≥3 episodes within 2 years), persistent symptoms >3 months, history of complicated diverticulitis, immunocompromised status, and patient preferences—not solely on the number of episodes. 4, 3

Elective sigmoidectomy reduces the 5-year recurrence rate to 15% versus 61% with conservative management, but carries a 10% short-term complication rate and 25% long-term complications. 4, 3 The DIRECT trial demonstrated significantly better quality of life at 6 months and 5-year follow-up after elective surgery compared with continued conservative management. 4, 3

Postoperative mortality is 0.5% for elective colon resection and 10.6% for emergent colon resection. 2

---

Common Pitfalls to Avoid

• Do NOT prescribe antibiotics routinely for uncomplicated diverticulitis without high-risk features—this contributes to antibiotic resistance without clinical benefit. 4, 3
• Do NOT apply the "no antibiotics" approach to complicated diverticulitis (Hinchey 1b or higher with abscess formation)—the evidence specifically excluded these patients. 4, 3
• Do NOT assume all patients require hospitalization—most can be safely managed as outpatients with appropriate follow-up, resulting in substantial cost savings. 4, 3
• Do NOT withhold antibiotics without first confirming uncomplicated disease on CT imaging—all studies supporting observation required imaging to rule out complications. 4, 3
• Do NOT overlook immunocompromised patients—they ALWAYS require immediate antibiotics (10-14 days), a lower threshold for repeat imaging, and early surgical consultation regardless of other factors. 4, 3
• Do NOT stop antibiotics early if they are indicated, even if symptoms improve—complete the full course. 4, 3
• Do NOT delay surgical consultation in patients with frequent recurrences affecting quality of life. 4, 3

---

Special Populations

Immunocompromised Patients:

Require immediate antibiotic therapy for 10-14 days, a lower threshold for CT imaging and repeat imaging, and early surgical consultation regardless of other factors. 4, 3 Corticosteroid use specifically increases the risk of perforation and death. 4, 3 These patients may present with milder signs and symptoms despite more severe disease. 3

Elderly Patients (>65 years):

Require a lower threshold for antibiotic treatment and closer monitoring, even when other outpatient criteria are met. 4, 3 Age >80 years is an absolute indication for antibiotic therapy. 4, 3, 2

Pregnant Patients:

Require antibiotic therapy regardless of other factors. 4, 3, 2