What is the management of a perianal abscess?

Management of Perianal Abscess

The primary treatment for perianal abscess is prompt surgical incision and drainage, with consideration of fistula treatment during the same procedure if identified, to prevent recurrence and complications. 1, 2

Diagnosis

• Most common symptom is pain
• Physical findings include swelling, cellulitis, and exquisite tenderness
• Low abscesses (intersphincteric, perianal, ischiorectal) typically present with local symptoms
• High abscesses (submucosal, supralevator) may present with systemic symptoms and pain referred to perineum, low back, or buttocks
• Differential diagnosis includes anal fissure, thrombosed hemorrhoids, levator spasm, STDs, proctitis, and cancer 1

Imaging

• Not routinely required for typical presentations
• Consider MRI (preferred), endoanal/transperineal ultrasound, or CT scan for:
  • Atypical presentations
  • Suspected complex abscesses
  • Recurrent abscesses
• Note: Imaging should not delay surgical treatment when clear signs of perianal abscess are present 2

Surgical Management

Timing

• Emergent drainage (immediate) required for:
  • Patients with sepsis or septic shock
  • Immunocompromised patients
  • Diabetic patients
  • Diffuse cellulitis 2
• Urgent drainage (within 24 hours) for cases without above factors 2

Technique

1. Incision should be made over point of maximal fluctuance
2. Incision should be adequate (typically 1-2 cm) to allow complete drainage
3. For perianal abscesses, keep incision as close as possible to anal verge to minimize potential fistula length
4. Break up all loculations to ensure complete drainage
5. Large abscesses should be drained with multiple counter incisions rather than a single long incision 1, 2

Fistula Management

• Examine for presence of fistula tract during abscess drainage
• If low fistula not involving sphincter muscle is identified, consider primary fistulotomy during same procedure
• For fistulas involving sphincter muscle, consider placing a loose draining seton 2
• Evidence shows fistula treatment with abscess drainage significantly reduces recurrence rates (RR=0.13,95% CI 0.07-0.24) 3

Antibiotic Therapy

• Not routinely indicated for uncomplicated perianal abscesses with adequate drainage
• Indicated in the following scenarios:
  • Systemic signs of infection
  • Immunocompromised patients
  • Incomplete source control
  • Significant surrounding cellulitis 1

Recommended Regimens (when indicated)

• Broad-spectrum coverage of gram-positive, gram-negative, and anaerobic bacteria
• Severe cases: Piperacillin-tazobactam or imipenem
• Duration:
  • Immunocompetent, non-critically ill patients with adequate source control: 4 days
  • Immunocompromised or critically ill patients: Up to 7 days
  • Diabetic patients: 7-10 days (extend if signs of persistent infection) 2

Post-Operative Care

• Packing typically remains in place for 48-72 hours (remove no later than 5 days)
• Follow-up within 48-72 hours to assess adequacy of drainage and signs of infection
• Patient education on wound care 2
• Evidence regarding packing vs. no packing is limited, with some studies suggesting no clear difference in healing time 4

Risk Factors for Recurrence

• Inadequate drainage (most common cause)
• Unidentified or untreated fistula
• Comorbidities: inflammatory bowel disease, diabetes mellitus, malignancy 5
• Recurrence rates up to 44% with inadequate treatment 2

Prevention of Recurrence

• Complete breakup of all loculations
• Adequate incision size for drainage
• Identification and appropriate management of fistula tracts
• Optimal glucose control in diabetic patients
• Adequate perineal hygiene
• Follow-up for possible fistula development 2

Special Considerations

• Incision-seton method may be more effective than simple incision-drainage for high perianal abscesses, with higher cure rates and lower recurrence rates 6
• In children, laying open identified fistulous tracts during initial operation reduces recurrence (8% vs 24% when fistula not identified) 7

Caution: Perianal abscesses in elderly and diabetic patients carry significant risks including higher risk of necrotizing infections, fistula formation, and systemic infection/sepsis 2.