Loose Seton Management of Perianal Fistulas

Mechanism of Action

A loose seton does not alter the anatomical location of a fistula tract; it maintains drainage through the existing pathway and prevents progression to more complex fistulas. 1, 2
The seton keeps the existing fistula tract patent across the sphincter complex, thereby avoiding premature closure and reducing the risk of abscess formation. 1, 2
By allowing inflammation around the tract to subside while preserving drainage, a loose seton prevents recurrence of abscesses. 1, 2
Continuous drainage provided by a loose seton prevents the development of more complex fistula tracts. 1

The seton is threaded through the cutaneous opening, the established fistula tract, the mucosal opening into the rectum, and out the anal canal, following the pre‑existing anatomical course. 3
For a low trans‑sphincteric fistula, a loose, fine silastic seton should be placed through the existing tract. 1, 4
Adequate drainage of any associated abscess must be achieved before seton placement to ensure optimal outcomes. 1, 2

Cutting setons (sequential tightening every 3–4 weeks) are contraindicated because they produce a 57 % incontinence rate due to forced sphincter transection. 5, 4
The loose seton must remain loose and non‑cutting throughout treatment; tightening is not recommended. 1, 2