What is the recommended treatment for a patient with fistula-in-ano?

Treatment of Fistula-in-Ano

For simple low fistulas not involving sphincter muscle (subcutaneous/intersphincteric), perform fistulotomy at the time of abscess drainage; for all fistulas involving sphincter muscle, place a loose draining seton to prevent incontinence. 1, 2

Initial Assessment and Imaging

Obtain contrast-enhanced pelvic MRI as the initial imaging modality to define fistula anatomy, identify occult abscesses, and assess for complex tracts. 1 If rectal stenosis is excluded, endoscopic anorectal ultrasound is an acceptable alternative. 1 The combination of imaging with examination under anesthesia (EUA) by an experienced surgeon increases diagnostic accuracy and remains the gold standard for anatomic definition. 1

Perform proctosigmoidoscopy routinely to evaluate for concomitant rectosigmoid inflammation, as this has both prognostic and therapeutic implications, particularly in Crohn's disease patients. 1

Classification and Treatment Strategy

Fistulas are classified as either simple (subcutaneous, low intersphincteric, or low transsphincteric in lower third of sphincter) or complex (high transsphincteric, suprasphincteric, extrasphincteric, or associated with proctitis). 1

Simple Fistulas (Low, Not Involving Sphincter)

Perform fistulotomy immediately by laying open the tract with debridement for subcutaneous or superficial fistulas. 1 This achieves healing rates exceeding 95% with minimal recurrence. 3

Critical caveat: Do not probe for occult fistulas during abscess drainage to avoid iatrogenic tract creation. 1

Complex Fistulas (Involving Sphincter Muscle)

Place a loose draining seton as the initial intervention for any fistula involving sphincter muscle. 1, 2 This prevents abscess recurrence, allows inflammation to subside, and facilitates personal hygiene while definitive treatment is planned. 1

The seton serves multiple purposes:

• Drains sepsis and prevents recurrent abscess formation (occurs in >66% of fistula patients) 1
• Maintains tract patency while medical therapy is optimized 1
• May be definitive treatment when combined with optimal medical therapy, with seton removal possible in up to 98% at median 33 weeks 1

Definitive Surgical Options for Complex Fistulas

Once sepsis is controlled and inflammation subsides, sphincter-saving techniques are mandatory for complex fistulas. 1, 3

Optimal outcomes are achieved with:

• Ligation of intersphincteric fistula tract (LIFT): Healing rates 60-90% 3
• Rectal advancement flap: Healing rates 60-90% 1, 3

Alternative sphincter-saving techniques include:

• Fistula laser closure (FiLaC): Healing rates 65-90% 3
• Video-assisted anal fistula treatment (VAAFT): Healing rates 65-90% 3
• Fibrin glue and collagen plugs: Variable outcomes 4

Important consideration: The choice among these techniques depends on fistula anatomy (location of openings, trajectory, complexity), presence of proctitis, and severity of anal canal disease. 1

Medical Therapy Integration

For Crohn's disease-related fistulas, medical therapy is essential:

• Seton placement with antibiotics (metronidazole and/or ciprofloxacin) as first-line for symptomatic simple fistulas 1
• Thiopurines, infliximab, or adalimumab for maintenance therapy or refractory disease 1
• Combination of seton drainage and medical therapy provides optimal outcomes 1

Medical therapy must control disease-related inflammation before and after surgery to increase likelihood of tract healing. 1

Antibiotic Therapy

Antibiotics are indicated in the following scenarios:

• Presence of sepsis or surrounding soft tissue infection 1
• Immunocompromised patients or diabetes 1
• Sample drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 1

Antibiotics are NOT routinely required after simple abscess drainage in immunocompetent patients without cellulitis. 1

Monitoring Treatment Response

Clinical assessment (decreased drainage) is sufficient for routine monitoring. 1

MRI or anal endosonography combined with clinical assessment should be used to evaluate fistula tract inflammation improvement when considering definitive closure procedures. 1

Management of Refractory Cases

For patients refractory to medical and surgical treatment:

• Consider diverting ostomy as next step 1
• Proctectomy is the last resort for intractable disease 1

Critical Pitfalls to Avoid

• Never perform fistulotomy on fistulas involving sphincter muscle - this causes incontinence in 1-2% of cases 5
• Do not surgically treat concomitant perianal skin tags in Crohn's patients - this leads to chronic non-healing ulcers 1
• Avoid probing for fistulas during acute abscess drainage - this creates iatrogenic tracts 1
• Do not attempt definitive fistula closure in the presence of active proctitis - control inflammation medically first 1