What is the recommended management of a perianal abscess?

Management of Perianal Abscess

Immediate incision and drainage is the mandatory treatment for all perianal abscesses, with timing dictated by the presence of sepsis, immunosuppression, diabetes, or extensive cellulitis. 1, 2

Surgical Drainage: The Cornerstone of Treatment

Timing of Intervention

Emergency drainage (within hours) is required for: 2

• Sepsis, severe sepsis, or septic shock
• Immunocompromised patients (including those on immunosuppressive therapy)
• Diabetes mellitus
• Diffuse cellulitis extending beyond the abscess

For stable, immunocompetent patients without these risk factors, drainage should still occur within 24 hours to minimize complications. 2 Bedside drainage in the emergency department for small, uncomplicated abscesses significantly shortens waiting time (2.13 vs. 10.41 hours) without increasing recurrence rates. 3

Surgical Technique

Keep the incision as close as possible to the anal verge to minimize potential fistula tract length while ensuring complete drainage. 1, 2 This is critical because inadequate drainage is the primary cause of recurrence, with rates reaching 44% when drainage is insufficient. 2

For large abscesses, use multiple counter-incisions rather than a single long incision to avoid step-off deformity and promote faster healing. 2

Location-Specific Approaches

• Perianal and ischioanal abscesses: Drain through overlying skin 2
• Intersphincteric abscesses: Drain into the rectal lumen to protect sphincter integrity 2
• Supralevator abscesses: Individualize based on origin—drain via rectal lumen if extending from intersphincteric space, or externally if extending from ischioanal space 2

Management of Fistulas During Drainage

If a low fistula not involving sphincter muscle is identified, perform fistulotomy at the same operative session. 2 However, if the fistula involves any sphincter muscle, place only a loose draining seton and defer definitive repair. 2

Do not probe for fistulas when none is apparent—this causes iatrogenic injury without benefit. 2 The practice of routinely searching for fistula tracts does not reduce recurrence rates. 4

Antibiotic Therapy

Antibiotics are NOT routinely indicated after adequate surgical drainage. 2 This is a critical point where practice often deviates from evidence.

Indications for Antibiotics

Use antibiotics only in these specific situations: 2

• Sepsis or systemic signs of infection
• Surrounding soft tissue infection or extensive cellulitis
• Immunocompromised patients
• Incomplete source control (residual undrained collections)

Antibiotic Selection and Duration

When antibiotics are indicated, use empiric broad-spectrum coverage for gram-positive, gram-negative, and anaerobic organisms, as these infections are polymicrobial. 2

Piperacillin-tazobactam 3.375g IV every 6 hours provides comprehensive coverage. 2 For recurrent cases, add MRSA coverage with vancomycin or linezolid, as MRSA prevalence can reach 35% in perirectal abscesses. 2

Duration: 5-10 days following operative drainage, with total therapy of 7-10 days for most cases. 2 Meta-analysis shows antibiotics reduce fistula formation by 36% (OR 0.64), though this benefit applies primarily to high-risk patients. 5

Post-Operative Care and Follow-Up

Routine imaging after drainage is not required. 2 Consider follow-up imaging only for: 2

• Recurrence
• Suspected inflammatory bowel disease
• Evidence of fistula or non-healing wound

The role of wound packing remains controversial, with some evidence suggesting it adds cost and pain without healing benefit. 2

Risk Factors for Recurrence

Be vigilant in patients with: 4, 6

• Crohn's disease (significantly increases recurrence risk)
• Active smoking
• Loculations or horseshoe-type abscess
• Short symptomatic period (<24 hours before presentation)
• Delayed time from onset to drainage

Recurrence rates range from 11-44% depending on these factors, with fistula formation occurring in 6-24% of cases. 4, 3, 6 Notably, surgeon experience level does not significantly alter recurrence rates—adequate drainage technique is what matters. 6

Special Considerations

For complex presentations (horseshoe abscesses, multiloculated collections, or suspected Crohn's disease), early colorectal surgery consultation is warranted. 2 If perianal Crohn's disease is suspected, perform endoscopic assessment of the rectum, as proctitis predicts persistent non-healing fistula tracts and higher proctectomy rates. 2

Common pitfall: Performing timid or overly small incisions leads to inadequate drainage and high recurrence—be aggressive with drainage while protecting sphincter anatomy. 2