What is the recommended management for perirectal abscesses?

Management of Perirectal Abscesses

The primary treatment for perirectal abscess is prompt surgical incision and drainage, which is essential for preventing complications and recurrence. 1

Diagnosis and Evaluation

• Clinical Assessment:

  • Primary symptom is pain (present in 98.9% of cases) 2
  • Physical findings include swelling, cellulitis, and exquisite tenderness 1
  • External perianal and digital rectal examination can identify an abscess in 94.6% of patients 2
  • Low abscesses typically present with local symptoms, while high abscesses may present with systemic symptoms and pain referred to perineum, low back, or buttocks 1

• Laboratory Investigations:

  • Check serum glucose, hemoglobin A1c, and urine ketones to identify undetected diabetes mellitus (strong recommendation) 3
  • In patients with signs of systemic infection or sepsis, obtain complete blood count, serum creatinine, and inflammatory markers (CRP, procalcitonin, lactates) 3

• Imaging:

  • Not routinely required for typical presentations 1
  • Consider MRI, CT scan with IV contrast, or endosonography in cases of:
    • Atypical presentation
    • Suspicion of occult supralevator abscesses
    • Complex anal fistula
    • Perianal Crohn's disease
    • Recurrent abscesses 3, 1

Surgical Management

• Incision and Drainage:

  • Make incision over point of maximal fluctuance
  • Ensure adequate incision size (typically 1-2 cm) to allow complete drainage
  • Break up all loculations to prevent recurrence
  • A #11 blade is preferred 1

• Timing of Surgery:

  • Base timing on presence and severity of sepsis 3
  • Emergent drainage (immediate) is required for:
    • Patients with sepsis or septic shock
    • Immunocompromised patients
    • Diabetic patients
    • Diffuse cellulitis 1
  • Urgent drainage (within 24 hours) for cases without the above factors 1
  • Outpatient management may be considered for fit, immunocompetent patients with small perianal abscesses without systemic signs of sepsis 3

• Fistula Management:

  • If a low fistula not involving sphincter muscle (subcutaneous fistula) is identified, perform fistulotomy at the time of abscess drainage 3
  • For fistulas involving any sphincter muscle, place a loose draining seton 3
  • Avoid probing to search for a fistula if not obvious, to prevent iatrogenic complications 3

Antibiotic Therapy

• Not routinely indicated for uncomplicated perianal abscesses with adequate drainage 1

• Indicated in:

  • Presence of sepsis
  • Surrounding soft tissue infection
  • Immunocompromised patients
  • Incomplete source control 3, 1

• Recommended Regimens:

  • First-line: Piperacillin/tazobactam 4g/0.5g q6h or 16g/2g by continuous infusion
  • For ESBL risk: Ertapenem 1g q24h or Eravacycline 1 mg/kg q12h
  • For septic shock: Meropenem, Doripenem, Imipenem/cilastatin, or Eravacycline 1

Post-Operative Care

• Follow-up within 48-72 hours to assess adequacy of drainage and signs of infection 1
• If packing is used, it typically remains in place for 48-72 hours and should be removed no later than 5 days 1
• Monitor for potential complications:
  • Recurrent abscess (occurs in up to 44% of cases)
  • Fistula formation
  • Urine retention 1, 2

Special Considerations

• High-Risk Patients:

  • Elderly patients, especially those with diabetes, have higher risk of necrotizing infections and systemic sepsis 1
  • Morbid obesity, preoperative sepsis, and dependent functional status are risk factors for reoperation 4
  • Female sex, steroid/immunosuppression, and dependent functional status are significant risk factors for readmission 4

• Crohn's Disease:

  • Perirectal abscesses in Crohn's disease patients are strongly associated with fistula formation
  • Requires extensive workup to determine the nature and extent of disease 5
  • Consider EUS-guided drainage as an alternative to conventional surgical drainage in selected cases 5

Prevention of Recurrence

• Ensure complete breakup of all loculations during initial drainage 1
• Optimal long-term glucose control in diabetic patients 1
• Maintain adequate perineal hygiene 1
• Consider fistula treatment at the time of abscess drainage, which significantly reduces recurrence (RR=0.13,95% CI = 0.07-0.24) 6