What is the recommended management of a psoas abscess in adult patients?

Management of Psoas Abscess in Adults

The recommended management of psoas abscess combines broad-spectrum intravenous antibiotics with source control via percutaneous catheter drainage (PCD) as first-line therapy, reserving surgical drainage for PCD failure or when percutaneous access is not feasible. 1, 2

Initial Diagnostic Approach

• Obtain CT imaging immediately for both diagnostic confirmation (92% sensitivity) and treatment planning 3
• Look specifically for: abscess size, extent, loculations, and any underlying pathology (vertebral osteomyelitis, urinary tract abnormalities, gastrointestinal source) 3, 2
• Send blood cultures and prepare for image-guided aspiration with culture 3, 4

Empirical Antibiotic Therapy

Start broad-spectrum IV antibiotics immediately—do not delay waiting for culture results. 3

Pathogen Coverage Required:

• Primary targets: E. coli and Klebsiella species (most common pyogenic causes) 3
• Also cover: Gram-positive organisms (including Staphylococcus aureus), Gram-negatives, and anaerobes 1, 2
• Reasonable initial regimens: Third-generation cephalosporins or fluoroquinolones with anaerobic coverage 3
• Consider tuberculous etiology if patient has risk factors or imaging suggests chronic process (tuberculous abscesses represent up to 92.8% in some series) 2

Critical Pitfall:

• Never use oral nitrofurantoin—it is contraindicated for psoas abscess 3
• Urine cultures may be negative in 28% of cases despite active infection, so negative cultures should not delay treatment 3

Source Control Strategy: Size-Based Algorithm

For Abscesses >5 cm:

Percutaneous catheter drainage (PCD) is the preferred first-line intervention 3, 4

• Perform under CT or ultrasound guidance 5, 4
• Insert drainage catheter and maintain until output is <10 mL for 48 hours 4
• Success rate: 71-100% in published series 5, 2, 4
• Average drainage duration: approximately 8 days 4

For Abscesses <4-5 cm:

• May attempt antibiotic therapy alone with close monitoring 1
• Requires serial imaging to confirm resolution 3
• Low threshold to proceed with drainage if no clinical improvement within 24-48 hours 5

When to Proceed Directly to Surgical Drainage

Consider open or laparoscopic/retroperitoneoscopic drainage when: 6, 2

• PCD fails (no clinical improvement within 24-48 hours) 5
• Percutaneous access is impossible due to anatomical constraints 6
• Multiple loculations present that cannot be adequately drained percutaneously 1, 2
• Concomitant pathology requires surgical intervention (e.g., vertebral debridement, bowel perforation) 6
• Recurrence after initial PCD (recurrence rates up to 44% with inadequate drainage) 1

Surgical Approach Options:

• Retroperitoneoscopic drainage: Minimally invasive, 1.8% recurrence rate, no major complications in systematic review of 56 patients 2
• Laparoscopic drainage: Complete drainage possible, allows tissue resection, faster recovery than open surgery 6
• Open surgical drainage: Reserved for complex cases or when minimally invasive approaches fail 7, 5

High-Risk Populations Requiring Aggressive Management

Lower threshold for early drainage intervention in: 3

• Diabetes mellitus patients 3, 1
• Immunosuppressed patients (HIV, transplant, chemotherapy) 7, 1
• Nephrolithiasis or urinary tract obstruction 3
• Anatomical urinary tract abnormalities 3
• Signs of sepsis, severe sepsis, or septic shock 1

Duration of Antibiotic Therapy

• 7 to 14 days total duration adjusted based on clinical response 3
• Expect clinical improvement within 24-48 hours of adequate drainage 5, 4
• Continue antibiotics until: fever resolves, inflammatory markers normalize, and follow-up imaging shows abscess resolution 3

Monitoring and Follow-Up

• Assess clinical response at 24-48 hours: improvement in pain, fever resolution, decreased inflammatory markers 5, 4
• If no improvement by 48 hours, consider PCD failure and proceed to surgical drainage 5
• Obtain follow-up imaging to confirm abscess resolution before discontinuing antibiotics 3, 4
• Long-term follow-up (up to 2 years) recommended to detect late recurrence 2, 4

Key Pitfalls to Avoid

• Inadequate drainage is the primary cause of treatment failure and recurrence 1
• Failure to identify underlying source (vertebral osteomyelitis, Crohn's disease, diverticulitis) leads to recurrence 7, 2
• Delayed intervention in septic patients increases mortality risk 7, 1
• Relying solely on antibiotics for large abscesses (>5 cm) results in treatment failure 3, 4