What is the treatment for a rectal abscess?

Treatment of Rectal Abscess

Surgical incision and drainage is the definitive treatment for all rectal abscesses and should be performed promptly to prevent systemic infection and complications. 1, 2

Immediate Surgical Management

All rectal abscesses require surgical drainage regardless of size or location. 1, 2 The surgical approach should follow these principles:

• Keep the incision as close as possible to the anal verge to minimize the length of any potential fistula tract while ensuring adequate drainage 2, 3
• Use multiple counter incisions for large abscesses rather than a single long incision to prevent step-off deformity and delayed wound healing 4, 2
• Time the surgery based on sepsis severity: patients with systemic signs of infection, immunosuppression, diabetes, or diffuse cellulitis require emergent drainage 2, 3
• Small perianal abscesses in fit, immunocompetent patients without systemic signs can be managed in an outpatient setting 2, 3

Fistula Management During Drainage

During the drainage procedure, examine for an associated fistula tract, but avoid aggressive probing if a fistula is not obvious as this causes iatrogenic complications 1:

• If a low subcutaneous fistula not involving sphincter muscle is identified, perform fistulotomy at the time of abscess drainage 1, 2
• If the fistula involves sphincter muscle, place a loose draining seton rather than performing immediate fistulotomy to prevent incontinence 1, 2, 3

Antibiotic Therapy

Antibiotics are NOT routinely indicated after adequate surgical drainage in immunocompetent patients. 1, 2 However, antibiotic therapy is mandatory in specific situations:

Indications for Antibiotics:

• Presence of sepsis or systemic signs of infection 1, 2
• Immunocompromised patients 1, 2
• Incomplete source control 4, 2
• Significant surrounding cellulitis 4, 2

Antibiotic Selection:

When antibiotics are indicated, use empiric broad-spectrum coverage targeting Gram-positive, Gram-negative, AND anaerobic bacteria. 4, 1, 2 This is critical because:

• Mixed aerobic/anaerobic organisms are present in 37% of cases, with additional mixed aerobic organisms in 33% 5
• Inadequate antibiotic coverage results in a six-fold increase in readmission rates (28.6% vs 4%) for abscess recurrence 5
• Sample drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 1

Diagnostic Workup

Essential Initial Assessment:

• Perform digital rectal examination to diagnose the abscess 1
• Check for undetected diabetes mellitus by measuring serum glucose, hemoglobin A1c, and urine ketones, as diabetes is a common comorbidity 1
• For patients with systemic infection or sepsis, obtain complete blood count, serum creatinine, and inflammatory markers (C-reactive protein, procalcitonin) 1

Imaging Considerations:

Imaging is not routinely required but should be obtained in specific circumstances 1, 2:

• Atypical presentation 1, 2
• Suspected occult supralevator abscesses 1, 2
• Suspected perianal Crohn's disease 1
• Preferred modalities: MRI, CT scan, or endosonography 1, 2

Critical Pitfalls to Avoid

The most dangerous complication is necrotizing soft-tissue infection, which carries a 40% mortality rate when sepsis is present at admission 6. Warning signs include:

• Rapidly spreading infection requiring frequent examinations under anesthesia 6
• Need for wide debridement, triple antibiotic therapy, and potentially diverting colostomy 6

Recurrence rates after drainage alone can reach 44% 2, 3, with risk factors including:

• Inadequate drainage 2, 3
• Loculations 2, 3
• Horseshoe-type abscess 2, 3
• Delayed time from disease onset to incision 2, 3

Follow-up Care

• Close follow-up is essential to monitor for recurrence or fistula development 2
• No definitive recommendation exists regarding wound packing after drainage 1
• Routine imaging after drainage is not required unless there is recurrence, suspected inflammatory bowel disease, or evidence of fistula/non-healing wound 2