What is the treatment for perianal Crohn's disease?

Treatment of Perianal Crohn's Disease

Infliximab is the first-line biologic therapy for perianal Crohn's disease, to be started as soon as adequate drainage of sepsis is achieved. 1

Initial Management Algorithm

1. Drainage of Perianal Abscess

   • Drainage is essential as the first step to control sepsis before adjusting immunosuppressive therapy 2
   • Radiologically guided drainage is recommended where possible 1
   • Surgery should be avoided for at least 2 weeks after percutaneous drainage 1

2. Antibiotic Therapy

   • Start broad-spectrum antibiotics after drainage:
     • Metronidazole 750-1500 mg/day or
     • Ciprofloxacin 1000 mg/day for up to 3-4 months 1
   • While antibiotics alone show no benefit for fistula remission, they play a role in managing acute sepsis 1

3. Medical Therapy

   • First-line therapy: Infliximab 5 mg/kg at weeks 0,2, and 6, then every 8 weeks 1, 3
     • Higher serum trough levels (>10 μg/mL) are associated with better outcomes 1
     • For patients who lose response, consider increasing to 10 mg/kg 3
   • Second-line options (for infliximab-refractory or intolerant patients):
     • Adalimumab (low-quality evidence) 1

Treatment Based on Fistula Classification

Simple Perianal Fistulas

• Antibiotics for initial treatment
• Consider fistulotomy for patients who don't respond to antibiotics 1
• Infliximab for patients who fail these initial approaches 1

Complex Perianal Fistulas

• Infliximab as first-line therapy 1
• Consider seton placement if fistula tract is identified during drainage 2
• Avoid surgical procedures like hemorrhoidectomy or fissure repair due to high complication rates 1

Combination Therapy Considerations

• Thiopurine monotherapy (azathioprine, 6-mercaptopurine) is not recommended for fistula closure 1
• Combination of infliximab with immunomodulators may be beneficial but has insufficient evidence specifically for perianal disease 1
• Caution with combination therapy due to increased risk of infections and possibly lymphoma 3

Special Situations

• Pregnant women: Those with active perianal Crohn's disease should undergo cesarean section 1
• Refractory disease: Consider early defunctioning ostomy for severe, rapidly progressive, or debilitating disease 1

Monitoring and Follow-up

• Reassess in 1-2 weeks after drainage and antibiotic therapy 2
• Consider MRI pelvis to evaluate for fistula tracts if symptoms persist 2
• Monitor for:
  • Recurrent abscess formation
  • Development of fistula tracts
  • Adverse effects of antibiotics
  • Systemic infection while on immunosuppression 2

Pitfalls and Caveats

• Patients who do not respond to infliximab by week 14 are unlikely to respond with continued dosing 3
• Surgical procedures like hemorrhoidectomy and fissure repair have high complication rates in Crohn's patients 1
• Purified protein derivative skin testing should be performed before starting infliximab due to risk of tuberculosis reactivation 1
• Cancer surveillance is important as squamous cell carcinoma, basal cell carcinoma, and adenocarcinoma can develop in chronic perianal fistula tracts 1

The management of perianal Crohn's disease requires a combined medical and surgical approach, with infliximab being the cornerstone of therapy after adequate drainage of sepsis.