Seton Re-routing for High Perianal Fistula

High perianal fistulae involve a significant portion of the external anal sphincter muscle, making standard surgical fistulotomy risky due to the potential for postoperative fecal incontinence. Sphincter-preserving techniques aim to eradicate the fistula tract and promote healing while safeguarding anal continence. The purpose of this prospective, single-arm clinical study is to evaluate the efficacy and safety of the two-stage seton re-routing technique in adult patients diagnosed with high perianal fistula at Assiut University Hospital. The procedure is conducted in two stages: * First Stage: Identification and curettage of the fistula tract followed by placement of a loose draining seton to clear local sepsis and allow fibrous maturation over an interval of 6 to 12 weeks. * Second Stage: Creation of a low submucosal or intersphincteric tunnel beneath the main external anal sphincter complex. The seton is unthreaded and re-routed through this lower pathway, isolating the upper transsphincteric tract so it can heal spontaneously by secondary fibrosis. The resulting downstaged superficial tract is then laid open (low fistulotomy) or managed with staged seton tightening. Participants will be monitored weekly during the first month, followed by regular monthly follow-up visits for a minimum of 6 to 9 months postoperatively. The study assesses complete fistula healing, recurrence rates, healing time, operative duration, postoperative complications, and anal continence status evaluated using the Cleveland Clinic (Wexner) Incontinence Score preoperatively and at 3, 6, and 9 months after surgery.