Seton Placement for Anal Fistula

Indications and Technical Specifications

The American College of Surgeons recommends loose, non-cutting setons for anal fistulas involving sphincter muscle, particularly in emergency settings or with abscess drainage, to establish drainage and prevent recurrent abscess formation while preserving continence 1
In the emergency setting, a loose draining seton should be inserted immediately if an obvious fistula exists during abscess drainage, without probing or attempting to lay the fistula open 1
More than two-thirds of patients with fistulas have an associated abscess that must be drained before any definitive intervention 2
The European Society of Coloproctology recommends placing setons in symptomatic patients with no concomitant abscess, medically controlled proctitis, and preferably an anatomically defined fistula tract 3, 4
Before any form of treatment, sepsis must be drained using loose setons to allow inflammation around the tract to subside and prevent abscess recurrence 3, 4
A loose, low-profile seton made of soft material, such as fine silastic setons, should be used 1
The seton should be placed through the fistula tract running through the sphincter complex ending in the internal opening to maintain drainage 3

Cutting setons are strongly contraindicated due to a 57% incontinence rate from transection and scarring of the anal sphincter 5, 6, 7
Anterior fistulas in female patients should never undergo fistulotomy due to asymmetrical anatomy and short anterior sphincter, which creates high risk of fecal incontinence 5, 6, 7
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
Combine seton drainage with antibiotics (metronidazole and/or ciprofloxacin) as first-line therapy for symptomatic simple perianal fistulas 4

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
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 5, 6, 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 5, 6, 7

Setons remain in place for variable durations ranging from 3 weeks to 40 months depending on the clinical scenario, with no standardized replacement schedule, as reported by the Journal of Crohn's and Colitis 8, 9
The European Crohn's and Colitis Organisation (ECCO) emphasizes that setons should be left in place until at least the anti-TNF induction phase is completed and proctitis has resolved, to prevent recurrent perianal abscess, with a new abscess rate of 15% when removed at week 2 10, 8

For patients with Crohn's disease, the ECCO-ESCP consensus recommends keeping the seton in place until at least the anti-TNF induction phase is completed and proctitis has resolved, to achieve optimal outcomes 10, 8, 9
For non-Crohn's fistulas, the optimal timing for seton removal is uncertain and should be based on clinical assessment of drainage adequacy, symptom control, and fistula complexity, as stated in Gut 11

The ECCO guidelines recommend never using cutting setons, which require tightening every 3-4 weeks and carry a 57% incontinence rate from sphincter transection 10, 8, 9
The American Gastroenterological Association (AGA) suggests avoiding routine replacement without clinical indication, as this subjects patients to unnecessary procedures, as reported in Gut 11

Loose seton drainage alone achieves fistula closure in 13.6-100% of cases, with high heterogeneity in studies, as reported in the Journal of Crohn's and Colitis 8, 9
Combined seton drainage with anti-TNF therapy produces better results than either modality alone, with a significant reduction in recurrence rates, as reported in the Journal of Crohn's and Colitis 8, 9