Treatment of Fistulas: Evidence-Based Approach
Critical First Step: Determine Fistula Type and Location
The optimal treatment for fistula depends entirely on whether you are dealing with a perianal/anorectal fistula (most commonly from Crohn's disease or cryptoglandular infection) versus a genitourinary fistula (vesicovaginal or enterovesical), as these require completely different management strategies.
Perianal/Anorectal Fistulas
Initial Assessment
Before any treatment, you must perform examination under anesthesia (EUA) to definitively classify the fistula, and obtain contrast-enhanced pelvic MRI to identify occult abscesses and define anatomy 1, 2. Fistulography is not recommended 1. Always perform proctosigmoidoscopy to assess for concomitant rectosigmoid inflammation, as active proctitis is a contraindication to definitive repair 1, 2.
Simple Perianal Fistulas
For simple low intersphincteric or low transsphincteric fistulas, initiate a short course of antibiotics (metronidazole 400-500 mg three times daily and/or ciprofloxacin 500 mg twice daily), and if no response, proceed to fistulotomy 1, 2. Fistulotomy achieves healing rates exceeding 95% with low recurrence 3.
- For patients who fail antibiotics or have recurrent disease, second-line options include azathioprine/6-mercaptopurine or infliximab 1
- Tacrolimus and cyclosporine are contraindicated in simple fistulas due to toxicity 1
Complex Perianal Fistulas
If an abscess or anorectal mass is present, medical therapy without surgical drainage is absolutely contraindicated 2. You must first drain any abscess and place a loose non-cutting seton 1, 2.
After drainage and seton placement, initiate combination therapy with infliximab (3-dose induction at weeks 0,2, and 6, then maintenance every 8 weeks) plus an immunosuppressor (azathioprine, 6-mercaptopurine, or methotrexate) 1, 4, 2. This combination is FDA-approved and has proven efficacy in placebo-controlled trials for both fistula reduction and maintenance 1.
- Antibiotics should be used adjunctively but have high relapse rates when used alone 1
- Azathioprine/6-mercaptopurine are slow-acting and better for maintenance than induction 1
- Concomitant immunosuppression is required to prevent human antichimeric antibodies that cause infusion reactions and loss of efficacy 1
Sphincter-saving surgical techniques (LIFT procedure, rectal advancement flaps) achieve healing rates of 60-90% but should only be performed after medical control of luminal inflammation and endoscopic mucosal healing 1, 3.
Critical Pitfalls to Avoid
- Never perform definitive fistula repair in the presence of active proctitis—control inflammation first 2
- Never start infliximab without first draining associated abscesses 4, 2
- Never discontinue immunosuppressors after achieving clinical closure—maintenance therapy is mandatory to prevent recurrence 1, 4
- Never assume clinical closure equals complete healing—high recurrence risk exists without complete tract fibrosis 4
Enterovesical Fistulas (Rectovesical/Colovesical)
Begin with medical therapy using infliximab plus immunosuppressor, as 65.9% of enterovesical fistulas respond completely to medical management 4. This is the appropriate initial approach before considering surgery.
Surgery is indicated only when medical therapy fails, or when complications develop including bowel obstruction, abscess formation, ureteral obstruction, or recurrent urinary tract infections 4.
Critical Considerations
- Always exclude malignant fistula before initiating anti-TNF therapy—malignant fistulas require oncologic resection, never local repair 4
- Anti-TNF agents have no role in malignant fistulas and delay definitive oncologic treatment 4
- Sigmoid origin carries higher surgical risk than small bowel origin 4
Vesicovaginal Fistulas
The majority of complex vesicovaginal fistulas can be successfully managed by transvaginal repair, which is minimally invasive with low costs and high cure rates (100% in recent series) 5.
- Transvaginal approach is preferred for most cases unless concomitant ureteral reimplantation or bladder augmentation is required 5, 6
- Transabdominal approach is reserved for specific indications including radiation-induced fistulas, large defects, or need for ureteral reimplantation 5, 6
- Timing of surgery, vascularized graft interposition, and surgical expertise are determining factors for success 6
- Fistulogram is the gold standard for evaluation in dialysis patients; use non-nephrotoxic contrast, carbon dioxide, or ultrasound in non-dialysis patients 7
Adjunctive Measures for All Fistulas
Control active luminal Crohn's disease with appropriate medical therapy (budesonide, corticosteroids, azathioprine, methotrexate, infliximab) and treat postoperative diarrhea with loperamide, diphenoxylate-atropine, codeine, cholestyramine, or low-fat diet to reduce stool liquidity and decrease fistula drainage 1.