What are the treatment options for complex perianal fistulas?

Treatment Options for Complex Perianal Fistulas

Infliximab combined with immunomodulators is the first-line treatment for complex perianal fistulas, with surgical seton placement as an essential adjunctive therapy for optimal outcomes. 1

Diagnosis and Assessment

Before initiating treatment, proper assessment is crucial:

• First-line imaging: Contrast-enhanced pelvic MRI 1
• Alternative imaging: Endoscopic anorectal ultrasound (if no rectal stenosis) 1
• Gold standard assessment: Examination under anesthesia (EUA) by experienced surgeon 1
• Required evaluation: Proctosigmoidoscopy to assess rectal inflammation 1

Classification of Perianal Fistulas

Complex perianal fistulas are defined as:

• High fistulas involving significant portions of sphincter
• Multiple fistula tracts
• Fistulas associated with rectal inflammation
• Rectovaginal fistulas 2, 1

Treatment Algorithm

Step 1: Control Sepsis

• Drain any perianal abscess before initiating immunosuppressive therapy 1, 3
• Place seton for initial drainage and to prevent abscess formation 1, 4

Step 2: Medical Management

• First-line medical therapy:

  • Infliximab (5 mg/kg at weeks 0,2, and 6, followed by maintenance every 8 weeks) 2, 1
  • Combined with immunomodulators (azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day) to reduce immunogenicity and improve efficacy 2, 1
  • Adjunctive antibiotics (metronidazole and/or ciprofloxacin) 1

• For patients failing infliximab:

  • Consider tacrolimus or cyclosporine in selected patients who fail multimodality treatment 2
  • Note: These agents have significant nephrotoxicity and other side effects 2

Step 3: Surgical Options

• Maintain setons during initial medical therapy 1

• For patients without rectal inflammation, consider:

  • Mucosal advancement flap
  • Ligation of intersphincteric fistula tract (LIFT)
  • Fibrin glue or fistula plug 1

• For rectovaginal fistulas:

  • Ensure endoscopic healing of rectosigmoid mucosa before surgical repair
  • Options include transanal or transvaginal advancement flaps 2

• Last resort options:

  • Fecal diversion (temporary ileostomy or colostomy)
  • Proctectomy 2, 1

Important Considerations and Pitfalls

• Never excise perianal skin tags in Crohn's disease as this can lead to chronic, non-healing ulcers 1
• Avoid simple hemorrhoidectomy in patients with Crohn's disease due to high risk of complications 1
• Fistulotomy should rarely be used for complex fistulas due to sphincter injury risk 1
• Maintenance therapy is essential for sustained fistula closure 1
• Recognize that more than two-thirds of patients have an abscess associated with their fistula that must be drained before any definitive intervention 1
• Despite optimal management, complete healing may not be achieved in all patients, with studies showing persistent fistulas in up to 58% of cases despite combined medical-surgical approaches 5

Special Considerations for Rectovaginal Fistulas

• Medical therapy options include 6-mercaptopurine, infliximab, cyclosporine, and tacrolimus 2
• Surgical repair should only be performed after endoscopic healing of rectosigmoid mucosa 2
• Some women may choose to accept residual fistula drainage over proctectomy with ostomy to optimize quality of life 2

The management of complex perianal fistulas requires a systematic approach combining medical and surgical interventions, with infliximab plus immunomodulators as the cornerstone of therapy, supplemented by appropriate surgical interventions based on fistula characteristics and patient factors.