Treatment of Fistulas
Initial Assessment and Classification
The treatment approach for fistulas depends critically on the type and location—perianal/anorectal fistulas require a fundamentally different strategy than vesicovaginal or arteriovenous fistulas, with perianal fistulas being the most common and requiring immediate assessment for sepsis. 1
For Perianal/Anorectal Fistulas
Obtain contrast-enhanced pelvic MRI as the initial imaging procedure to define fistula anatomy and identify occult abscesses. 1 Endoscopic anorectal ultrasound is an acceptable alternative if rectal stenosis is excluded. 1
Perform examination under anesthesia (EUA) by an experienced surgeon—this is the gold standard for assessment. 1
Always perform proctosigmoidoscopy to evaluate for concomitant rectosigmoid inflammation, as this has major prognostic and therapeutic implications. 1
Classify fistulas as either:
- Simple: Low intersphincteric or low transphincteric fistulas 1
- Complex: High transphincteric, suprasphincteric, extrasphincteric, rectovaginal, or those associated with Crohn's disease 1, 2
Treatment Algorithm for Simple Perianal Fistulas
Rule out and drain any perianal abscess immediately—more than two-thirds of patients have an associated abscess that must be drained before definitive intervention. 1, 2
For uncomplicated low anal fistulas, simple fistulotomy may be performed after confirming no abscess is present. 1
For symptomatic simple fistulas, the preferred first-line strategy is seton placement combined with antibiotics (metronidazole and/or ciprofloxacin). 1
If the simple fistula is refractory to antibiotics and seton drainage:
- Add thiopurines (azathioprine or 6-mercaptopurine) as second-line therapy 1
- Consider anti-TNF agents (infliximab or adalimumab) as second-line therapy 1
Treatment Algorithm for Complex Perianal Fistulas
Step 1: Emergency Management
Immediately drain any abscess via EUA and place a loose (non-cutting) seton to maintain drainage and prevent recurrent abscess formation. 1, 2
Step 2: Medical Optimization
Start antibiotics (metronidazole and/or ciprofloxacin) in combination with seton drainage. 1
Treat active luminal Crohn's disease if present—active proctitis is an absolute contraindication to definitive closure procedures. 1, 2
Optimize medical therapy with thiopurines, infliximab, or adalimumab before considering any definitive surgical closure. 1, 2
Step 3: Definitive Surgical Options (Only After Inflammation Control)
Once sepsis is controlled and inflammation is optimized, consider:
- Mucosal advancement flap: 64% success rate but carries 9.4% incontinence risk and 50% require re-intervention 2
- LIFT procedure (ligation of intersphincteric fistula tract): 56-94% healing rate, best results in primary cases 2
- Fibrin glue: Variable success, generally lower than other options 1, 2
- Fistula plug: 24-88% success, but 22% dislodgement rate; suturable bioprosthetic plugs show 87% closure when they remain in place 2
Never perform fistulotomy on complex or high fistulas—this carries an unacceptable risk of fecal incontinence. 2
Step 4: Maintenance Therapy
Use thiopurines, infliximab, or adalimumab as maintenance therapy, or continue seton drainage long-term, or combine both approaches. 1
Special Considerations for Crohn's Disease-Associated Fistulas
Never excise perianal skin tags in Crohn's patients—this leads to chronic non-healing ulcers. 1, 2
For rectovaginal fistulas in Crohn's disease, medical therapy with anti-TNF agents shows effectiveness in up to 45% of cases. 3
Surgical repair of rectovaginal fistulas should only be performed after endoscopic healing of rectosigmoid mucosa, using transanal or transvaginal advancement flaps. 3
Infliximab is FDA-approved for fistulizing Crohn's disease with a 3-dose induction regimen (5 mg/kg at weeks 0,2, and 6) followed by maintenance dosing every 8 weeks. 4 In clinical trials, 68% of patients achieved fistula response (≥50% reduction in draining fistulas) with 5 mg/kg infliximab versus 26% with placebo. 4 At 54 weeks, 38% of infliximab-treated patients had complete closure of all fistulas compared to 22% with placebo. 4
Salvage Options for Refractory Cases
For severe, therapy-refractory disease not responding to medical and surgical treatment, consider diverting ostomy. 3, 2 Diverting stoma achieves early remission in up to 81%, but sustained remission occurs in only 26-50%, with most patients ultimately requiring proctectomy. 2
Proctectomy with permanent stoma is reserved as a last resort for severe disease with irreversible perineal destruction. 3, 2
Treatment of Vaginal Fistulas
Rectovaginal Fistulas
Control underlying inflammation first with medical therapy, particularly in Crohn's disease, before attempting surgical repair. 3
Asymptomatic low anal-introital fistulas may not require surgical treatment. 3
For symptomatic rectovaginal fistulas with healed rectal mucosa, perform transanal or transvaginal advancement flap repair. 3
Vesicovaginal Fistulas
The majority of complex vesicovaginal fistulas can be successfully managed by vaginal repair, which is minimally invasive with low costs and high cure rates (100% success in recent series). 5
Use abdominal approach for vesicovaginal fistulas requiring concomitant ureteral re-implantation or bladder augmentation. 5
Enterovaginal Fistulas
Enterovaginal fistulas often require resective surgery, especially when associated with abscess, bowel stricture, or causing excessive diarrhea and malabsorption. 3
Monitoring Treatment Response
Clinical assessment of decreased drainage is usually sufficient to evaluate healing in routine practice. 1, 2
Add MRI or anal endosonography to clinical assessment when you need to evaluate improvement of fistula tract inflammation. 1, 2
Remember that clinical closure does not equal MRI closure—there is high risk of recurrence without complete fibrotic tract on MRI. 3
Critical Pitfalls to Avoid
Never attempt definitive closure without first controlling sepsis and inflammation. 2
Never proceed with definitive surgery in Crohn's patients with active proctitis. 2
Never perform fistulotomy on high or complex fistulas due to unacceptable incontinence risk. 2
Always drain abscesses before considering any operative intervention beyond seton placement. 1, 2