What is the recommended management for a large presacral abscess with suspected intraspinal extension and communication with the anal canal?

Management of Large Presacral Abscess with Intraspinal Extension and Anal Canal Communication

This patient requires emergency surgical drainage given the large size (49mm), suspected intraspinal extension, and communication with the anal canal, combined with broad-spectrum antibiotics covering polymicrobial organisms. 1, 2

Immediate Management Algorithm

Urgent Surgical Intervention Required

Emergency drainage is mandatory for this patient based on multiple high-risk features 1, 2:

• Large abscess size (49mm) requires complete drainage with multiple counter incisions rather than single incision to prevent step-off deformity and ensure adequate drainage 2
• Suspected intraspinal extension represents a neurosurgical emergency requiring immediate decompression to prevent permanent neurological deficit 3
• Communication with anal canal at 6-7 o'clock position indicates complex fistulizing disease requiring specialized colorectal surgical expertise 1, 4
• Possible bony erosions of coccyx suggests advanced infection requiring debridement 5, 6

Surgical Approach Selection

The surgical approach must be individualized based on the intraspinal extension:

For confirmed intraspinal extension:

• Trans-sacral-foramen approach is the shortest, safest path for presacral abscesses with epidural involvement 5, 6
• CT-guided percutaneous transsacral drainage using 8G bone marrow biopsy needle to create path, followed by 8Fr drainage catheter placement via Seldinger technique 6
• This approach is minimally invasive and may be the only viable option for lumbosacral junction involvement 6

For the anal canal communication component:

• Simultaneous drainage via rectal approach for the anal canal communication 2, 4
• Place a loose draining seton for the fistula tract involving the external anal sphincter rather than immediate fistulotomy to prevent incontinence 1, 4
• Do NOT probe for additional fistulas during acute drainage as this causes iatrogenic complications 1, 4

Antibiotic Therapy

Empiric broad-spectrum antibiotics are mandatory given the size, complexity, and intraspinal extension 2, 4:

• Coverage must include Gram-positive, Gram-negative, and anaerobic bacteria as these abscesses are polymicrobial 2
• Sample drained pus for culture and sensitivity, particularly given the complex nature and risk for multidrug-resistant organisms 1, 4
• Continue antibiotics until clinical improvement and reduction in abscess size on follow-up imaging 5, 6

Critical Pitfalls to Avoid

Incomplete drainage is the primary cause of recurrence (up to 44% recurrence rate with inadequate drainage) 2, 7:

• Ensure complete evacuation of all loculations 2, 7
• Multiple counter incisions may be needed for large abscesses rather than single long incision 2
• Leave drainage catheter in place until pus output significantly reduces (typically 2 weeks) 5, 6

Do not delay drainage for imaging if not immediately available, though in this case MRI has already been performed 2

Do not attempt fistulotomy of the sphincter-involving fistula during acute drainage - only place seton 1, 4

Post-Drainage Management

• No wound packing recommended as evidence suggests it is costly and painful without added benefit 2, 4
• Monitor for neurological symptoms given the intraspinal extension 3
• Follow-up MRI at 2 weeks to assess abscess reduction 5, 6
• Remove drainage catheter only after significant reduction in pus output and clinical improvement 5, 6

Underlying Etiology Considerations

Evaluate for Crohn's disease given the complex fistulizing nature and presacral location 2, 8, 9:

• Check serum glucose, HbA1c, and urine ketones to identify undetected diabetes 1, 4
• Consider endoscopic assessment of rectum if Crohn's disease suspected, as proctitis predicts persistent non-healing fistula tracts 2
• Inflammatory markers (CRP, procalcitonin) should be obtained given the systemic nature 1, 4