What is the recommended management for a patient presenting with an anal fistula, specifically regarding seton placement?

Seton Placement for Anal Fistula

Loose, non-cutting setons should be placed in all anal fistulas involving sphincter muscle, particularly in the emergency setting or when associated with abscess drainage, to establish drainage and prevent recurrent abscess formation while preserving continence. 1

Indications for Seton Placement

Emergency/Acute Setting

• Insert a loose draining seton immediately if an obvious fistula exists during abscess drainage, without probing or attempting to lay the fistula open. 1
• Do not actively search for an associated fistula during initial abscess presentation, as over-vigorous probing creates iatrogenic tracks and internal openings that complicate future management. 1
• More than two-thirds of patients with fistulas have an associated abscess that must be drained before any definitive intervention. 2

Elective Setting

• Place setons in symptomatic patients with no concomitant abscess, medically controlled proctitis, and preferably an anatomically defined fistula tract. 3
• Before any form of treatment (medical or surgical), sepsis must be drained using loose setons to allow inflammation around the tract to subside and prevent abscess recurrence. 3

Technical Specifications

Seton Material and Configuration

• Use a loose, low-profile seton made of soft material, such as fine silastic setons. 1
• Avoid bulky knots and firm suture materials such as nylon. 1
• The seton should be placed through the fistula tract running through the sphincter complex ending in the internal opening to maintain drainage. 3

Critical Contraindications

Never Use Cutting Setons

• Cutting setons are strongly contraindicated due to a 57% incontinence rate from transection and scarring of the anal sphincter. 3
• Despite nearly 100% fistula closure rates, the high risk of permanent incontinence makes this technique unacceptable. 3

Avoid Fistulotomy When:

• Any sphincter muscle involvement is present or suspected. 1
• Moderate to severe proctitis complicates the fistula. 1
• The fistula is located in the upper two-thirds of the sphincter complex. 1
• Anterior fistulas in female patients should never undergo fistulotomy due to asymmetrical anatomy and short anterior sphincter, which creates high risk of fecal incontinence. 3

Seton as Definitive Treatment

Efficacy

• Loose setons combined with optimal medical therapy can be definitive treatment, with seton removal achieved in up to 98% of patients at a median of 33 weeks. 3, 1
• In a multicenter study of 200 patients, all patients achieved successful fistula clearance with loose seton placement, with 96% tolerating the procedure well. 4
• Healing rates of 78% were achieved with median healing time of 9 weeks, with no patients developing fecal incontinence. 5

Special Considerations for Crohn's Disease

Initial Management

• Perform adequate surgical drainage of perianal abscess without searching for an associated fistula. 1
• Insert a loose draining seton if an obvious fistula exists, without probing. 1
• If moderate to severe proctitis complicates a fistula, seton placement is the only sensible option, and medical therapy must be commenced to treat proctitis. 3

Medical Therapy Integration

• Combine seton drainage with antibiotics (metronidazole and/or ciprofloxacin) as first-line therapy for symptomatic simple perianal fistulas. 3
• For recurrent refractory disease not responding to antibiotics, use thiopurines or anti-TNF agents as second-line therapy. 3
• Maintain therapy with thiopurines, infliximab, or adalimumab in combination with seton drainage. 3

Timing of Seton Removal in Crohn's Disease

• Keep the seton in place until at least the induction phase of anti-TNF treatment is completed (approximately one month) and resolution of proctitis is achieved. 3
• Removing the seton too early results in high risk of recurrent perianal abscess (15% new abscess rate when removed at Week 2). 3
• Leaving the seton too long may cause tract epithelialization and prevent fistula closure. 3

Postoperative Management

Wound Care

• Clean the perianal area gently after each bowel movement using warm water without harsh soaps. 6
• Perform sitz baths with warm water for 10-15 minutes, 2-3 times daily. 6
• Apply non-adherent dressing if significant drainage occurs to prevent skin maceration. 6
• The seton should remain properly positioned to maintain drainage; patients should not attempt to remove or adjust it. 6

Monitoring

• Clinical assessment of decreased drainage is usually sufficient to evaluate treatment response. 6
• Regular evaluation for signs of infection, excessive inflammation, or abscess formation is essential. 6
• MRI or anal endosonography combined with clinical assessment can evaluate fistula tract inflammation improvement if needed. 6

Warning Signs Requiring Immediate Attention

• Increasing pain, swelling, or redness around the perianal area. 6
• Fever or signs of systemic infection. 6
• Significant increase in drainage or purulent discharge. 6

Long-Term Outcomes and Prognosis

Success Rates

• Recurrence rate with loose seton placement is 6% in large series. 4
• For Crohn's disease patients, long-term seton drainage preserves sphincter function, though recurrence is common (39%) if the seton is removed. 7
• A small percentage of patients with extensive aggressive disease uncontrolled by medical management and long-term seton placement may require diversion or proctectomy. 3

Continence Preservation

• When sphincter muscle is not divided with loose seton drainage, minor incontinence develops in only 26-36% of patients, compared to 54% with cutting techniques. 7
• Faecal diversion is effective in reducing symptoms in two-thirds of perianal Crohn's disease patients and may improve quality of life, but only one-fifth remain stoma-free long-term. 3