What are the treatment options for perirectal fistula?

Treatment for Perirectal Fistula

The optimal treatment for perirectal fistula requires a combined surgical and medical approach, starting with seton placement followed by anti-TNF therapy, with subsequent surgical closure in the absence of proctitis. 1

Initial Assessment and Classification

Before initiating treatment, proper evaluation is essential:

• Imaging: Contrast-enhanced pelvic MRI is the first-line diagnostic procedure 1
• Endoscopic evaluation: Proctosigmoidoscopy to assess for rectal inflammation 1
• Examination under anesthesia (EUA): Gold standard for definitive assessment 1
• Classification: Fistulas are generally categorized as simple or complex 1

Treatment Algorithm

Step 1: Control Sepsis and Create Patent Tract

• Drainage of any associated abscess is mandatory 1
• Seton placement to maintain drainage and prevent abscess recurrence 1

Step 2: Medical Therapy

• First-line medical therapy: Anti-TNF agents (preferably infliximab) with high trough levels 1
  • Infliximab dosing: 5 mg/kg at weeks 0,2, and 6, then every 8 weeks 2
  • Clinical response rates up to 60% with medical therapy alone 1
• Adjunctive antibiotics: Metronidazole and/or ciprofloxacin 1
• Maintenance therapy options:
  • Thiopurines (azathioprine, 6-mercaptopurine) 1
  • Consider combination therapy with anti-TNF and immunomodulators 1

Step 3: Surgical Closure (After Medical Optimization)

• Timing: Consider seton removal within 2-8 weeks after good response to anti-TNF therapy 1
• Surgical options based on fistula type:
  • Simple fistulas (intersphincteric or low trans-sphincteric): Fistulotomy 1
  • Complex fistulas: Advancement flap (AF) or ligation of intersphincteric fistula tract (LIFT) 1
  • Alternative techniques: Video-assisted anal fistula treatment (VAAFT), fibrin glue, fistula plug 1, 3, 4

Special Considerations

Rectovaginal Fistulas

• Require endoscopic healing of rectosigmoid mucosa before surgical repair 1
• Surgical options include transanal/transvaginal advancement flaps or primary closure 1
• Consider patient preferences regarding quality of life vs. complete healing 1

Treatment-Refractory Cases

• For anti-TNF failure: Consider alternative biologics (vedolizumab, ustekinumab) 1
• For surgically refractory fistulas: Experimental approaches like hyperbaric oxygen therapy 1
• Stem cell therapy: Allogeneic adipose-derived stem cells show promise, particularly for patients with multiple internal openings or pre-existing incontinence 1, 3
• Last resort options: Diverting ostomy or proctectomy 1

Monitoring Response

• Clinical assessment (decreased drainage) is usually sufficient for routine practice 1
• MRI or anal endosonography can evaluate improvement in fistula track inflammation 1
• Complete MRI closure is rare with medical therapy alone (<10%) but more common after surgical closure under anti-TNF therapy (up to 40%) 1

Pitfalls and Caveats

• Avoid treating perianal skin tags surgically as this can lead to chronic, non-healing ulcers 1
• Despite optimal treatment, perianal fistulas may persist in up to 58% of patients 5
• MRI closure rates are significantly lower than clinical closure rates 1
• Recurrence rates are high after medical therapy alone, with frequent need for surgical reintervention 1
• Patients with rectal inflammation (proctitis) have lower rates of fistula healing 1