What is the recommended treatment for a perianal abscess?

Perianal Abscess Treatment

Immediate incision and drainage under general anesthesia is mandatory for every perianal abscess—antibiotics alone will fail. 1, 2

Timing of Surgical Intervention

Emergency drainage within hours is required for:

• Sepsis, severe sepsis, or septic shock 1, 2
• Immunosuppression (steroids, chemotherapy, HIV) 1, 2
• Diabetes mellitus 1, 2
• Diffuse cellulitis or extensive soft tissue infection 1, 2

For all other patients, perform drainage within 24 hours of presentation. 2

Exception for Bedside Drainage

• Small, superficial abscesses in young, fit, immunocompetent patients without systemic signs may be drained at bedside under local anesthesia 2, 3
• This approach shortens time to intervention (2 hours vs. 10 hours) without increasing recurrence rates 3

Surgical Technique

Incision placement:

• Make the incision as close as possible to the anal verge to minimize future fistula tract length while ensuring complete drainage 1, 2
• For large abscesses, use multiple counter-incisions rather than one long incision to avoid step-off deformity 2

Location-specific approaches:

• Perianal and ischioanal abscesses: Drain via overlying skin incision 1, 2
• Intersphincteric abscesses: Drain into the rectal lumen, possibly with limited internal sphincterotomy 2
• Supralevator abscesses: Drain via rectal lumen if intersphincteric extension, or externally if ischioanal extension 2

Critical technical point: Inadequate drainage is the principal cause of recurrence—recurrence rates jump from 15% with adequate drainage to 44% with inadequate drainage. 2 Thoroughly evacuate all pus and break up all loculations. 2

Management of Concomitant Fistulas

Do NOT probe for a fistula when none is clinically evident—probing causes iatrogenic injury without reducing recurrence. 1, 2 Approximately one-third of perianal abscesses have an associated fistula, but probing in the acute, edematous setting is contraindicated. 2

If an obvious fistula is identified without probing:

• Low fistula not involving sphincter muscle: Perform immediate fistulotomy 1, 2
• Any fistula involving sphincter muscle: Place a loose draining seton only and defer definitive repair 1, 2

Advanced fistula repair techniques (fibrin glue, fistula plug, LIFT, advancement flap, VAAFT, FiLac, stem-cell therapy) have no role in the emergency setting. 2

Antibiotic Therapy

Routine antibiotics are NOT indicated after adequate surgical drainage in immunocompetent patients. 1, 2

Prescribe antibiotics ONLY when:

• Clinical sepsis or systemic signs of infection present 1, 2
• Extensive cellulitis spreading beyond the abscess cavity 1, 2
• Documented immunocompromise 1, 2
• Incomplete source control (residual undrained collections) 2

When antibiotics are required:

• Use empiric broad-spectrum coverage targeting Gram-positive, Gram-negative, and anaerobic organisms (polymicrobial infection) 2
• Obtain pus cultures in high-risk patients or when multidrug-resistant organisms suspected 2
• Consider MRSA coverage in recurrent cases (prevalence up to 35% in perirectal abscesses) 2

Post-Operative Care

Wound packing is NOT routinely recommended—evidence shows it increases cost and pain without improving healing rates. 2 Reserve packing only for short-term hemostasis at clinician's discretion. 2

Routine post-operative imaging is NOT required. 2 Reserve imaging for:

• Suspected recurrence 2
• Concern for inflammatory bowel disease 2
• Non-healing wounds or suspected persistent fistula 2

Intra-Operative Assessment

Perform examination under anesthesia to:

• Identify occult fistulous openings (present in ~33% of cases) 2
• Assess the rectal mucosa for signs of proctitis—proctitis predicts persistent non-healed fistula tracts and higher proctectomy rates 2

Special Populations

Crohn's disease patients:

• Perform adequate drainage without searching for an associated fistula 1
• If obvious fistula present, insert loose draining seton but do not lay open 1
• Assess rectum for proctitis during drainage 1

Diabetic patients:

• Screen for glycemic control (glucose, HbA1c, urine ketones) 4
• Require emergency drainage within hours 2

Common Pitfalls to Avoid

• Inadequate drainage: Failure to evacuate all pus and break up loculations is the primary cause of recurrence 2
• Probing for fistulas: Causes iatrogenic injury without benefit when no fistula is clinically apparent 1, 2
• Delaying drainage for imaging: Clinical examination identifies >94% of perirectal abscesses; do not delay definitive treatment 2
• Routine antibiotic prescription: Contributes to antimicrobial resistance without improving outcomes after adequate drainage 2
• Attempting advanced fistula repair in acute setting: Results in failure and potential harm when sepsis present 2