What is the treatment for a perianal abscess?

Treatment of Perianal Abscess

The primary treatment for perianal abscess is surgical incision and drainage, ideally performed within 24 hours of presentation, with careful examination for underlying fistulas during the procedure. 1

Diagnosis and Assessment

• Initial evaluation:

  • Physical examination to assess for pain, erythema, warmth, fluctuance, and systemic symptoms
  • Differentiate from hematoma based on progressive pain, significant erythema, marked warmth, and systemic symptoms 1

• Imaging:

  • Pelvic MRI is the gold standard for detailed assessment (76-100% accuracy) 2, 1
  • Endoscopic assessment of the rectum is essential to determine management strategy and assess for proctitis 2
  • Ultrasound is useful for initial differentiation between hematoma and abscess 1

• Examination under anesthesia (EUA):

  • Experienced colorectal surgeons can achieve up to 90% accuracy in detecting and classifying perianal fistulas and abscesses 2
  • Should not be delayed if MRI is not immediately available when abscess is suspected 2

Surgical Management

• Incision and drainage:

  • Primary treatment for all perianal abscesses 1
  • Emergent drainage indicated for patients with sepsis, immunosuppression, diabetes mellitus, or diffuse cellulitis 1
  • Complete and thorough drainage is essential to prevent recurrence 1

• Fistula management:

  • Up to one-third of perianal abscesses have an underlying fistula-in-ano 1, 3
  • Carefully search for underlying fistula during drainage procedure 1
  • Consider placing a loose draining seton for suspected sphincteric muscle involvement 1
  • Meta-analysis shows significant reduction in recurrence when fistula is treated at the time of abscess drainage (RR=0.13,95% CI 0.07-0.24) 3
  • Avoid probing or using hydrogen peroxide to search for fistulas to prevent iatrogenic complications 1

Antibiotic Therapy

• Indications for antibiotics:

  • Patients with sepsis, surrounding soft tissue infection, or immunocompromised status 1
  • Should cover Gram-positive, Gram-negative, and anaerobic bacteria 1

• For perianal abscesses in Crohn's disease:

  • Metronidazole (10-20 mg/kg daily) and ciprofloxacin (20 mg/kg daily) are recommended 1
  • Metronidazole is indicated for various anaerobic infections including intra-abdominal abscesses, skin and skin structure infections 4

Post-Operative Care

• Wound care:

  • Clean the wound with warm water/saline 2-3 times daily 1
  • Consider sitz baths for perianal abscesses 1
  • Use non-adherent absorbent dressings 1
  • Consider alginate or hydrofiber dressings for deeper wounds 1

• Follow-up:

  • First follow-up within 48-72 hours after drainage 1
  • Subsequent follow-ups every 1-2 weeks until complete healing 1
  • Monitor for signs of recurrent abscess formation, development of fistula, delayed healing, and signs of infection 1
  • Monitor inflammatory markers (CRP, WBC count) and procalcitonin levels if initially elevated 1

Special Considerations

• Crohn's disease patients:

  • Active luminal disease should be treated concurrently with surgical management 1
  • For complex fistulas, consider infliximab, azathioprine, or 6-mercaptopurine along with antibiotics 1
  • Long-term seton placement with medical therapy may be beneficial for complex fistulas 1

• Risk factors for recurrence:

  • Inadequate initial drainage 1
  • Presence of loculations 1
  • Delayed time from disease onset to incision 1
  • Underlying conditions such as Crohn's disease 1
  • Untreated underlying fistula 3

Complications and Their Prevention

• Fistula formation:

  • Antibiotics may reduce post-operative fistula formation 1
  • Careful assessment for fistulas during initial procedure is critical 1

• Incontinence risk:

  • Excessive division of the internal anal sphincter carries risk of fecal incontinence 1
  • Particular caution needed with high intersphincteric abscesses 1
  • No statistically significant evidence of incontinence following fistula surgery with abscess drainage (pooled RR 3.06,95% CI 0.7-13.45) 3