Treatment of Anorectal Abscess
Surgical incision and drainage is the definitive treatment for all anorectal abscesses and should be performed urgently, with timing based on the severity of sepsis. 1, 2
Initial Diagnostic Approach
Clinical Assessment
- Perform digital rectal examination to identify the abscess location and assess for fluctuance 1
- Screen for undetected diabetes mellitus by checking serum glucose, hemoglobin A1c, and urine ketones, as diabetes is a common comorbidity in these patients 1, 2
Laboratory Testing
- If the patient shows signs of systemic infection or sepsis, obtain complete blood count, serum creatinine, and inflammatory markers (C-reactive protein, procalcitonin, lactate) 1, 2
- These tests help stratify severity and guide timing of intervention 1
Imaging Considerations
- Imaging is NOT routinely required for straightforward perianal abscesses 2
- Consider MRI, CT scan, or endosonography only in these specific scenarios: 1, 2
- Atypical presentation
- Suspected occult supralevator abscess
- Concern for complex anal fistula
- Known or suspected perianal Crohn's disease
Surgical Management
Timing and Setting
- Emergent drainage is required for patients with sepsis, immunosuppression, diabetes, or diffuse cellulitis 3
- Base surgical timing on the presence and severity of sepsis 1, 2
- Exception: Fit, immunocompetent patients with small perianal abscesses and no systemic signs can be considered for outpatient management 1, 3
Surgical Technique
- Make the incision as close as possible to the anal verge to minimize the length of any potential fistula while ensuring adequate drainage 3
- For deeper or complex abscesses, more extensive drainage with multiple counter incisions may be required 2
- Avoid probing for a fistula if one is not obvious, as this causes iatrogenic complications 1, 2
Management of Concomitant Fistula
If an obvious fistula is identified at the time of drainage, follow this algorithm: 1, 2, 3
- Low subcutaneous fistula (not involving sphincter muscle): Perform fistulotomy at the time of abscess drainage
- Fistula involving any sphincter muscle: Place a loose draining seton rather than performing immediate fistulotomy to prevent incontinence
- No obvious fistula: Do not probe to search for one
Antibiotic Therapy
Antibiotics are NOT routinely indicated for adequately drained anorectal abscesses in immunocompetent patients. 2
Indications for Antibiotics
Administer antibiotics only in these specific situations: 1, 2
- Presence of sepsis
- Surrounding soft tissue infection or diffuse cellulitis
- Immunocompromised patients
- Disturbances of immune response
Antibiotic Selection
- When indicated, use empiric broad-spectrum coverage for Gram-positive, Gram-negative, and anaerobic bacteria 2
- Sample drained pus for culture in high-risk patients or those with risk factors for multidrug-resistant organisms 1, 2
- Adjust therapy based on culture results if available 2
Post-Procedure Management
Wound Care
- No definitive recommendation exists regarding wound packing after drainage based on current evidence 1, 2
- This remains a clinical decision based on individual circumstances 1
Follow-Up Considerations
- Recurrence risk after drainage alone can be as high as 44%, emphasizing the need for complete and accurate initial drainage 3
- Risk factors for recurrence include inadequate drainage, loculations, horseshoe-type abscess, and delayed time from disease onset to incision 3
- Fistula formation occurs in 25-50% of cases and is more common with gut-derived organisms (E. coli, B. fragilis) 4, 5
Common Pitfalls to Avoid
- Do not delay drainage in patients with sepsis or immunosuppression—these require emergent intervention 3
- Do not perform immediate fistulotomy for fistulas involving sphincter muscle, as this risks incontinence 1, 3
- Do not probe blindly for fistulas if not obvious, as this creates iatrogenic tracts 1, 2
- Do not prescribe routine antibiotics after adequate drainage in immunocompetent patients without systemic infection 2