What is the management and workup for a patient with a suspected intra-abdominal abscess, particularly those with a history of abdominal surgery, trauma, or underlying conditions such as inflammatory bowel disease?

Management and Workup of Intra-Abdominal Abscess

For intra-abdominal abscesses >3 cm, perform CT-guided percutaneous drainage combined with empiric broad-spectrum antibiotics covering gram-negative aerobes, anaerobes, and streptococci; for abscesses <3 cm in stable patients, initiate empiric antibiotics alone with close monitoring; proceed to surgery immediately if septic shock is present or if percutaneous drainage fails. 1

Initial Diagnostic Workup

Clinical Assessment

• Fever (present in 97% of cases), localized abdominal tenderness (80%), and absence of generalized peritonitis are the key clinical features distinguishing drainable abscesses from those requiring immediate surgery. 2
• Pain and tenderness are the only clinical parameters that reliably differentiate patients with versus without abscesses. 3

Imaging Strategy

• CT scan is the single best imaging modality and should be the only radiologic test performed in most cases. 3
• CT demonstrates superior sensitivity, specificity, and accuracy compared to ultrasound or gallium scanning, with an accuracy rate of 0.86 when test results disagree. 3
• Multiple imaging tests are redundant in 72% of cases and do not improve diagnostic yield. 3

Treatment Algorithm Based on Abscess Size and Patient Stability

Abscesses >3 cm in Hemodynamically Stable Patients

• Perform CT or ultrasound-guided percutaneous drainage as first-line treatment, which achieves success rates of 74-100%. 1, 4
• Use anterior approach in 80% of cases; transgluteal window may be necessary for posterior collections. 2
• Percutaneous drainage serves as a bridge to elective surgery, reducing stoma creation rates and limiting intestinal resection in malnourished and high-risk patients. 1
• Primary success occurs in 65% after first drainage and 85% after second drainage attempt. 2

Abscesses <3 cm in Stable Patients

• Initiate empiric intravenous antibiotics alone with close clinical and biochemical monitoring. 1
• This approach carries high recurrence rates, especially if associated with enteric fistula. 1
• Non-drainable small abscesses without fistula and in patients not on steroids are most likely to respond to antibiotics alone. 1

Patients with Septic Shock or Hemodynamic Instability

• Proceed directly to surgical drainage—percutaneous approaches are contraindicated. 1
• Surgery is also indicated for generalized peritonitis. 2

Antibiotic Management

Empiric Regimen

• Administer fluoroquinolones or third-generation cephalosporin PLUS metronidazole to cover gram-negative bacteria, anaerobes, and streptococci. 1
• Start antibiotics early and adapt to microbiological culture results as soon as available. 1

Duration and Monitoring

• Clinical improvement should occur within 3-5 days of starting antibiotics and drainage. 1
• Re-evaluate with repeat imaging if no improvement occurs; consider drain repositioning or surgical intervention. 1
• Continue antibiotics until clinical and biochemical parameters normalize (monitor CRP levels). 1

Indications for Surgical Intervention

Immediate Surgery Required

• Septic shock or hemodynamic instability 1
• Generalized peritonitis 2
• Failure of percutaneous drainage 1

Delayed Elective Surgery Indicated

• Persistent sepsis despite initial treatment 1
• Enteric fistulae 1
• Concomitant stenosis or refractory active disease 1, 4
• Recurrent abscess after percutaneous drainage (occurs in higher rates with drainage alone versus initial surgery) 1

Risk Factors for Percutaneous Drainage Failure

Independent predictors of failure include: 1

• Bowel wall thickness
• Disease length
• Bowel dilation
• Abscess size >6 cm
• Multiple abscesses (8-20% require repeat drainage procedures)

Complications to Monitor

Percutaneous Drainage Complications (10% overall)

• Major complications (5-11%): sepsis, small bowel fistulae, colon perforation, death from sepsis or hemorrhage 1
• Minor complications (3%): bacteremia, catheter site infection 1

Surgical Considerations

• Preoperative percutaneous drainage reduces postoperative complications, stoma rates, and extent of intestinal resection compared to immediate surgery. 1
• Allows optimization of nutritional status and general condition before definitive surgery. 1

Special Populations

Inflammatory Bowel Disease Patients

• The presence of an abscess contraindicates immunosuppressive medication until infection is controlled. 1
• After successful drainage and sepsis control, restart IBD-specific medications to prevent recurrence. 1
• Preoperative immunomodulators, anti-TNF agents, and steroids increase risk of intra-abdominal sepsis in patients requiring emergency surgery. 1

Postoperative Abscesses

• Most appear within 8 weeks, but can present asymptomatically 3-5 years after colorectal surgery for inflammatory bowel disease. 5
• Percutaneous drainage achieves 87.5% resolution with single collections. 2

Multidisciplinary Approach

• Optimal management requires collaboration between gastroenterology and acute care surgery. 1
• All patients should receive adequate IV fluids, low-molecular-weight heparin for thromboprophylaxis, and correction of electrolyte abnormalities and anemia. 1