What is the recommended treatment for a perianal abscess?

Treatment of Perianal Abscess

Incision and drainage is the definitive treatment for perianal abscess and must be performed promptly—antibiotics alone are inadequate and will fail. 1, 2, 3

Surgical Drainage: The Cornerstone of Treatment

Timing of Intervention

• Emergency drainage (immediate) is required for patients with: 1, 2

  • Sepsis, severe sepsis, or septic shock
  • Immunosuppression
  • Diabetes mellitus
  • Diffuse cellulitis extending beyond the abscess

• Urgent drainage (within 24 hours) should be performed for all other patients once diagnosis is established 1, 2

• Do not delay drainage waiting for imaging if clinical diagnosis is clear—an undrained abscess will expand into adjacent spaces and progress to life-threatening systemic infection 2, 4

Surgical Technique Based on Abscess Location

The incision must be placed as close to the anal verge as possible to minimize potential fistula length while ensuring complete drainage. 1, 2, 3

• Perianal and ischioanal abscesses: Drain via incision through overlying skin 1, 2

• Intersphincteric abscesses: Drain into the rectal lumen; may require limited internal sphincterotomy 1, 2

• Supralevator abscesses: Drain via rectal lumen (if extension of intersphincteric abscess) or externally via skin (if extension of ischioanal abscess) 1, 2

• For larger abscesses: Create multiple counter incisions rather than a single long incision to prevent step-off deformity and delayed healing 2, 4

Critical Importance of Complete Drainage

Inadequate drainage is the primary cause of high recurrence rates. 1, 2 Needle aspiration has a 41% recurrence rate compared to 15% after proper incision and drainage 1. Risk factors for recurrence include loculations, horseshoe-type abscess, and delayed time from disease onset to incision 2, 3.

Management of Concomitant Fistulas

Decision Algorithm for Fistula Treatment

If an obvious fistula is identified during abscess drainage: 1, 2, 3

• Low fistula NOT involving sphincter muscle (subcutaneous): Perform fistulotomy at the time of abscess drainage—this reduces recurrence from 44% (drainage alone) to 21% (drainage with fistulotomy) 4, 5

• Fistula involving ANY sphincter muscle: Place a loose draining seton rather than performing immediate fistulotomy to prevent fecal incontinence 1, 2, 3, 4

• Do NOT probe to search for a fistula if none is obvious—this risks iatrogenic complications in the setting of acute infection and edema 1

The evidence strongly supports selective fistula treatment: a meta-analysis of 479 patients showed significant reduction in recurrence with fistula surgery (RR=0.13,95% CI 0.07-0.24) without statistically significant incontinence at one year 5.

Postoperative Wound Management

Packing: The Evidence Says Don't Do It

Avoid routine wound packing after perianal abscess drainage—it increases pain without improving outcomes. 2, 6

The highest quality evidence comes from the PPAC2 randomized trial of 433 patients, which demonstrated: 6

• Non-packing resulted in significantly lower pain scores (28.2 vs 38.2 on 100-point VAS, p<0.0001)
• No increase in fistula formation (11% vs 15%, p=0.20)
• No increase in abscess recurrence (6% vs 3%, p=0.20)

Alternative approaches if hemostasis or drainage support is needed: 1

• Place a catheter or corrugated rubber drain into the cavity with external dressing
• Remove when drainage stops

Antibiotic Therapy: When NOT to Use Them

Antibiotics are NOT routinely indicated after adequate surgical drainage in immunocompetent patients. 2, 3, 4

Specific Indications for Antibiotics

Use antibiotics ONLY when: 2, 3, 4

• Systemic signs of infection or sepsis are present
• Patient is immunocompromised
• Incomplete source control after drainage
• Significant surrounding cellulitis extending beyond abscess borders

Antibiotic Selection When Indicated

When antibiotics are necessary, use empiric broad-spectrum coverage targeting Gram-positive, Gram-negative, and anaerobic bacteria since these abscesses are frequently polymicrobial 2, 4

Setting for Procedure

• Outpatient/ambulatory setting with local anesthesia: Young, fit, immunocompetent patients with small simple perianal abscesses and no systemic sepsis 1, 3, 4

• Operating room under adequate anesthesia: Deeper or more complex abscesses (intersphincteric, supralevator, ischioanal) requiring thorough examination and complete drainage 3, 4

Follow-Up and Monitoring

Close follow-up is essential to monitor for recurrence or fistula development, as recurrence rates can reach 44% even with proper drainage 2, 3, 4

• Routine imaging after drainage is NOT required unless: 2, 3

  • Recurrence occurs
  • Inflammatory bowel disease is suspected
  • Evidence of fistula or non-healing wound

• If perianal Crohn's disease is suspected, perform endoscopic assessment of the rectum as proctitis predicts persistent non-healing fistula tracts 2

Common Pitfalls to Avoid

• Never rely on antibiotics without drainage—this will fail and allow progression to deeper infection 2, 4

• Never perform a single long incision for large abscesses—this creates deformity and delays healing 2, 4

• Never perform immediate fistulotomy if the fistula involves significant sphincter muscle—this risks permanent fecal incontinence; use a seton instead 1, 2, 3, 4

• Never prescribe antibiotics routinely after adequate drainage in healthy patients—this is unnecessary and promotes resistance 2, 3, 4

• Never pack the wound routinely—this increases pain without benefit 6