Management of Fistula in Ano
For any patient with fistula in ano, immediate surgical drainage of abscess (if present) followed by loose seton placement is the mandatory first step, with definitive treatment decisions deferred until sepsis is controlled and fistula complexity is fully mapped by pelvic MRI. 1, 2
Initial Assessment and Diagnosis
Examination under anesthesia (EUA) by an experienced surgeon is the gold standard for fistula assessment, as clinical examination alone frequently misses the true extent of disease 1, 2.
Obtain contrast-enhanced pelvic MRI before any surgical intervention to map fistula anatomy, identify occult abscesses, and distinguish simple from complex tracts 1, 2, 3. This is particularly critical in suspected Crohn's disease, where multiple fistulas at different positions strongly suggest inflammatory bowel disease rather than simple cryptoglandular infection 3.
Perform colonoscopy and proctosigmoidoscopy in all patients with complex or multiple fistulas to exclude Crohn's disease, as perianal fistulas can be the initial manifestation in up to 81% of Crohn's patients who develop perianal disease, even without bowel symptoms 2, 3. Active proctitis is an absolute contraindication to definitive fistula repair 2, 3.
Immediate Surgical Management
Drain any abscess immediately if present—medical therapy alone without drainage is contraindicated 2. More than two-thirds of transphincteric fistulas have an associated abscess that must be drained before considering any definitive intervention 1.
Place a loose (non-cutting) seton after abscess drainage to maintain drainage and prevent recurrent abscess formation 1, 2. This applies to all complex fistulas and is the only appropriate initial surgical treatment in the acute setting 2.
Treatment Strategy Based on Fistula Classification
Simple/Low Fistulas (Intersphincteric or Low Transphincteric)
Fistulotomy may be considered for uncomplicated low anal fistulas in cryptoglandular disease 3, 4. In strictly selected Crohn's patients with low-lying transphincteric fistulae, fistulotomy can achieve good healing rates with acceptable incontinence risk 5.
Seton placement combined with antibiotics (metronidazole 400-500 mg three times daily and/or ciprofloxacin 500 mg twice daily) is the preferred initial strategy even for simple fistulas when sphincter preservation is paramount 2, 3.
Complex/High Fistulas (High Transphincteric, Suprasphincteric, Extrasphincteric)
Never perform fistulotomy on complex or high fistulas—the incontinence risk is unacceptable 1. For high transphincteric fistulas, the only option is loose seton placement 5.
Long-term loose seton drainage combined with medical therapy is the cornerstone approach for high or complex transphincteric fistulas 1. The seton remains in place indefinitely while medical therapy is optimized 1.
Definitive Closure Options (After Sepsis Control)
Once inflammation and sepsis are controlled, consider these options in order of preference:
- LIFT procedure: 56-94% healing rate, with best results in primary (not recurrent) cases 1
- Mucosal advancement flap: 64% success rate (range 33-93%), but carries 9.4% incontinence risk and 50% require re-intervention 1
- Fistula plug: 24-88% success, but 22% dislodgement rate; suturable bioprosthetic plugs show 87% closure when they remain in place 1
- Fibrin glue: Generally lower success than other options 1
Special Management for Crohn's Disease
Optimize medical therapy before any definitive surgical intervention 1, 2. Anti-TNF therapy (infliximab or adalimumab) combined with immunomodulators (thiopurines) is first-line medical treatment after surgical drainage and seton placement 2, 3.
The combination of seton drainage plus anti-TNF therapy shows superior outcomes compared to either alone 1. Maintenance therapy with thiopurines, infliximab, adalimumab, seton drainage, or a combination is recommended 3.
Never excise perianal skin tags in Crohn's patients—this leads to chronic non-healing ulcers 1. Active proctitis must be medically controlled before attempting any definitive fistula repair 2, 3.
Salvage Options for Refractory Disease
Diverting stoma achieves early remission in up to 81% of refractory cases, but sustained remission occurs in only 26-50%, and most patients ultimately require proctectomy 1.
Proctectomy with permanent stoma is the last resort for severe, therapy-refractory perianal Crohn's disease 1, 6.
Monitoring Treatment Response
Clinical assessment of decreased drainage is usually sufficient to evaluate healing 1, 3. MRI or endoanal ultrasound can be added to clinical assessment if needed to evaluate fistula tract inflammation 1, 3.
Critical Pitfalls to Avoid
- Never attempt definitive closure without first controlling sepsis and inflammation 1
- Never proceed with definitive surgery in Crohn's patients with active proctitis 1, 2
- Do not rely on absence of bowel symptoms to exclude Crohn's disease—perianal manifestations can be isolated 3
- Never perform medical therapy alone without surgical drainage when an abscess or complex fistula is present 2