What are the guidelines for seton (a thin, flexible tube) insertion in a patient with an anal fistula, considering their medical history and potential complications?

Seton Insertion for Anal Fistula

Primary Recommendation

In patients with anal fistula, a loose draining seton should be inserted when there is an obvious fistula involving any sphincter muscle, particularly in the emergency setting or when associated with abscess drainage. 1

Indications for Seton Placement

Emergency/Acute Setting

• Insert a loose draining seton 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 may create iatrogenic tracks and internal openings that complicate future management. 1
• Only perform fistulotomy at the time of abscess drainage for subcutaneous fistulas not involving sphincter muscle. 1

Elective Setting

The appropriate indications for seton placement aiming to close a fistula include: 1

• Symptomatic patient
• No concomitant abscess present
• Medically controlled proctitis (if Crohn's disease)
• Preferably anatomically defined fistula tract

Technical Specifications

Seton Material and Configuration

• Use a loose, low-profile seton made of soft material (fine silastic setons are most commonly used). 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 to the internal opening to maintain drainage. 1

Seton Types and Their Purposes

Loose (non-cutting) setons are primarily used to: 1

• Establish drainage of the fistula
• Minimize risk of future abscess formation
• Facilitate personal hygiene
• Serve as definitive treatment when combined with optimal medical therapy

Contraindications to Immediate Fistulotomy

Do not lay open the fistula if: 1

• Any sphincter muscle involvement is present or suspected
• Moderate to severe proctitis complicates the fistula
• The fistula is located in the upper two-thirds of the sphincter complex
• Crohn's Disease Activity Index (CDAI) is greater than 150
• Evidence of perineal Crohn's disease involvement exists

Special Considerations for Crohn's Disease

Acute Management

• Perform adequate surgical drainage of perianal abscess without searching for an associated fistula. 1
• If an obvious fistula exists without probing, insert a loose draining seton rather than laying it open. 1
• No additional surgical fistula treatment modalities (fibrin glue, fistula plug, LIFT, advancement flap, VAAFT, FiLac, stem cells) should be attempted in the emergency setting when sepsis is present. 1

Maintenance Therapy

Combine seton drainage with medical therapy: 1, 2

• Thiopurines, infliximab, or adalimumab
• Antibiotics (metronidazole and/or ciprofloxacin) may be prescribed in combination with seton placement
• Medical therapy must be commenced to treat proctitis if present

Expected Outcomes

Efficacy

• Loose seton placement achieves successful clearance of fistula in all patients when properly managed. 3
• The seton may be removed in up to 98% of patients at a median of 33 weeks when used as definitive treatment with optimal medical therapy. 1
• Median healing time is approximately 9 weeks (range 4-62 weeks). 4

Tolerance and Safety

• The procedure is well tolerated in 96% of patients. 3
• No post-procedure complications or fecal incontinence when used appropriately. 4
• Fistula recurrence rate is approximately 6%. 3

Postoperative Management

Wound Care

• Clean the perianal area gently after each bowel movement using warm water without harsh soaps. 2
• Perform sitz baths with warm water for 10-15 minutes, 2-3 times daily. 2
• Apply non-adherent dressing if significant drainage occurs. 2
• The seton should remain properly positioned and not be removed or adjusted by the patient. 2

Monitoring

• Regular evaluation of the perianal area for signs of infection, excessive inflammation, or abscess formation. 2
• Monitor for decreased drainage as a positive sign of improvement. 2
• Clinical assessment of drainage is usually sufficient to evaluate treatment response. 2

Follow-up

• Regular follow-up appointments are essential to monitor healing and determine appropriate timing for seton removal. 2
• The median number of seton changes required is 3 (range 1-8), with mean interval between changes of approximately 3 months. 3

Warning Signs Requiring Immediate Attention

Seek medical attention for: 2

• Increasing pain, swelling, or redness around the perianal area
• Fever or signs of systemic infection
• Significant increase in drainage or purulent discharge
• Signs of recurrent abscess formation