What is the next step in management for a patient with left lower abdominal pain, high fever, and a 1 cm pericolonic collection on CT scan?

Management of Small Pericolonic Collection in Acute Diverticulitis

For a 60-year-old male with fever, left lower abdominal pain, and a 1 cm pericolonic collection on CT scan, the answer is B: IV antibiotics. This small abscess should be treated with intravenous antibiotics alone without percutaneous drainage.

Rationale for Antibiotic Therapy Alone

Small diverticular abscesses (<3 cm) should be managed with antibiotic therapy alone for 7 days, without drainage procedures. 1 The most recent Italian guidelines (2024) specifically state that antibiotic therapy alone is appropriate for small diverticular abscesses, while reserving percutaneous drainage for large abscesses 1. This is further supported by the 2017 WSES consensus, which established that a maximum diameter of 3-6 cm has been generally accepted as the reasonable limit for treatment with antimicrobial therapy alone without drainage 1.

Why Not Percutaneous Drainage?

• Percutaneous drainage is reserved for larger collections. The ACR Appropriateness Criteria (2020) recommend percutaneous catheter drainage combined with antibiotic therapy specifically for large diverticular abscesses, not small ones 1
• The 1 cm collection in this case is well below the 3 cm threshold where drainage becomes necessary 1
• For collections this small, antibiotics achieve high success rates without the risks and invasiveness of drainage procedures 1

Why Not Conservative Management Without Antibiotics?

• The presence of fever (high temperature) indicates complicated diverticulitis requiring antibiotic therapy 1
• Conservative treatment without antibiotics is only appropriate for uncomplicated diverticulitis without systemic signs of infection 1
• The pericolonic collection, even though small, represents an abscess that requires antimicrobial treatment 1

Why Not Colonoscopy?

• Colonoscopy is contraindicated in acute diverticulitis due to the risk of perforation from bowel insufflation 1
• Endoscopic evaluation should be deferred until the acute inflammatory process has resolved
• The diagnosis is already established by CT imaging 1

Recommended Antibiotic Regimen

For immunocompetent, non-critically ill patients with adequate source control:

• Antibiotic therapy should be administered for 7 days 1
• Empiric coverage should target gram-negative organisms and anaerobes 1
• Options include combination therapy with a cephalosporin plus metronidazole, or single-agent therapy with agents like ertapenem 1

Clinical Monitoring

• Close clinical and biochemical monitoring is essential during antibiotic therapy 1
• Patients who have ongoing signs of infection or systemic illness beyond 7 days warrant diagnostic investigation 1
• Follow-up imaging may be considered if clinical improvement does not occur within the expected timeframe 1

Common Pitfalls to Avoid

• Do not perform colonoscopy during the acute phase - this significantly increases perforation risk 1
• Do not withhold antibiotics in the presence of fever and abscess formation - even small collections require antimicrobial therapy when systemic signs are present 1
• Do not rush to drainage for collections <3 cm - this exposes patients to unnecessary procedural risks when antibiotics alone are effective 1