In a patient with right lower quadrant pain and a 15 × 12 cm appendiceal abscess extending to the abdominal wall, what is the most appropriate next step in management?

Management of Large Appendiceal Abscess

For a patient with a 15 × 12 cm appendiceal abscess extending to the abdominal wall, percutaneous drainage combined with antibiotics is the most appropriate next step in management. 1

Rationale for Percutaneous Drainage

The Surgical Infection Society and Infectious Diseases Society of America guidelines explicitly recommend percutaneous drainage (PCD) combined with antibiotics as the initial intervention for patients with acute appendicitis and a large abscess. 1 This approach is strongly supported by multiple high-quality guidelines:

• For collections >3 cm, PCD is strongly advocated over antibiotics alone, with efficacy rates of 70-90%. 2, 1
• PCD results in significantly lower complication rates and shorter hospital stays compared to immediate operative management. 2, 1, 3
• The American College of Radiology recommends CT guidance for deep collections, allowing safe access while avoiding adjacent structures. 2, 1

Why Not Immediate Surgery?

Attempting immediate appendectomy in the presence of a large, mature abscess increases morbidity without improving outcomes. 1 The evidence is clear:

• Immediate appendectomy for appendiceal abscess results in higher complication rates (58% vs. 15%) and longer hospital stays (14.8 vs. 9.0 days) compared to percutaneous drainage with interval appendectomy. 3
• When surgery is required after preliminary PCD, it significantly reduces postoperative septic complications and the ultimate need for stoma creation. 2

Technical Approach

Two drainage techniques are available with high success rates:

• Seldinger (wire-guided) or trocar (direct puncture) technique, with success thresholds of 95% for aspiration and 85% for catheter drainage. 2, 1
• The American College of Radiology recommends CT guidance for this size abscess extending to the abdominal wall. 2

Contraindications to Consider

Before proceeding with PCD, ensure the patient does NOT have:

• Peritoneal signs indicating diffuse peritonitis (the question states tenderness but not diffuse peritonitis). 2, 1
• Active hemorrhage or hemodynamic instability. 2, 1
• Lack of maturation of the abscess wall (this 15 cm abscess is clearly mature). 2, 1

Antibiotic Coverage

Initiate broad-spectrum IV antibiotics immediately that cover enteric gram-negative organisms and anaerobes:

• Single-agent regimens: piperacillin-tazobactam, ampicillin-sulbactam, ertapenem, or meropenem. 4
• Combination therapy: ceftriaxone + metronidazole OR ciprofloxacin + metronidazole. 4
• Continue for 3-5 days after adequate drainage and clinical resolution. 4

Expected Outcomes and Follow-up

• Approximately 80% of patients successfully treated with PCD do not require subsequent appendectomy. 1
• Timely drainage provides clear clinical benefit, though optimal timing remains debated. 2, 1
• Success rates for PCD in appendiceal abscess range from 74-100%. 2

Risk Factors for PCD Failure

Monitor closely for factors associated with drainage failure:

• Patient complexity and comorbidities. 1
• Abscess size >40 mm (this patient's 150 mm abscess warrants close monitoring). 5
• Low rate of improvement in WBC count on the first day of treatment. 5
• If clinical deterioration occurs despite drainage, conversion to surgery is mandatory. 2, 1

Common Pitfalls to Avoid

• Do not attempt laparoscopic appendectomy as the initial approach for this large, mature abscess—it increases morbidity without benefit. 1, 3
• Do not use antibiotics alone for collections >3 cm—this leads to treatment failure. 2, 1
• Do not delay drainage when technically feasible, as this allows progression of sepsis. 1