Patient-Reported Outcomes Following Loose Seton Material Replacement in Complex Anal Fistula

This prospective, single-center, self-controlled pilot cohort study evaluates whether loose seton biomaterial is associated with patient-reported outcomes in adults with recurrent or persistent complex cryptoglandular anal fistula. Participants with an existing polypropylene loose seton who require seton replacement as part of routine clinical management will be prospectively enrolled. The decision to replace the seton will be made by the treating colorectal surgeon independently of study participation. No seton replacement or additional surgical procedure will be performed solely for research purposes. Patient-reported outcomes will be assessed immediately before replacement while the polypropylene loose seton remains in place and will be reassessed at 4 and 12 weeks after replacement with a braided polyester loose seton. The primary outcome is the within-participant change in disease-specific quality of life measured using the Quality of Life in Patients with Anal Fistula Questionnaire (QoLAF-Q). Secondary outcomes include perianal pain, anal continence, patient comfort, foreign-body awareness, hygiene burden, anal discharge, interference with daily activities, patient satisfaction, analgesic use, and treatment-related adverse events. The study uses a within-participant design in which each participant serves as their own control. As a pilot study, it will also evaluate recruitment, retention, questionnaire completion, protocol adherence, and outcome variability to inform the design of a future multicenter prospective study.

Inclusion Criteria: * Age 18 years or older * Recurrent or persistent complex cryptoglandular anal fistula * Existing polypropylene loose seton in situ * Clinically indicated replacement of the polypropylene loose seton with a braided polyester loose seton as part of routine clinical management * Sufficient previous experience with the polypropylene loose seton to permit baseline assessment of patient-reported outcomes * Ability to understand and complete the study questionnaires * Provision of written informed consent Exclusion Criteria: * Anal fistula associated with Crohn's disease * Anal malignancy * Rectovaginal fistula * Acute perianal abscess or acute perianal sepsis requiring emergency surgical intervention * Cognitive impairment preventing completion of patient-reported outcome questionnaires * Inability to complete the study questionnaires * Pregnancy