Intraoperative Flexible Rectoscopy for Internal Opening Identification in Transsphincteric Perianal Fistula: A Feasible and Accessible Adjunct to Seton Placement

Background and Objectives: Accurate identification of the internal opening is a key determinant of success in perianal fistula surgery, as missed openings are strongly associated with persistent infection and recurrence. Although magnetic resonance imaging provides detailed preoperative mapping, intraoperative confirmation relies largely on surgical judgment. This study evaluated the technical feasibility and early observed outcomes of flexible rectoscopy-guided identification of the internal opening during loose seton placement in patients with transsphincteric perianal fistula whose internal opening could not be localized by routine assessment or pelvic MRI. Materials and Methods: This single-center retrospective descriptive feasibility series included 44 adult patients with cryptoglandular transsphincteric perianal fistula who underwent loose seton placement. All included patients had an internal opening that could not be localized by routine preoperative assessment or pelvic MRI. Intraoperative flexible rectoscopy was used to identify the internal opening in relation to the dentate line. The primary endpoint was successful intraoperative visualization of the internal opening. Operative time, healing time, early follow-up outcomes, Wexner continence score and patient satisfaction were descriptively recorded. Results: The mean age was 41.00 ± 12.06 years and the mean BMI was 29.86 ± 3.65 kg/m2. The internal opening was successfully visualized using flexible rectoscopy in all 44 patients (100%). Mean operative time was 6.66 ± 1.49 min and mean healing time was 59.45 ± 9.96 days. During the available 3–7-month early follow-up, no complications were documented, while recurrence occurred in one patient (2.3%) at the fourth postoperative month. The exact binomial 95% confidence interval for the observed recurrence rate was 0.06–12.02%. The median postoperative Wexner score was 0 (IQR 0–0; range 0–1). Conclusions: Flexible rectoscopy enabled intraoperative identification of the internal opening in all patients in this descriptive series and may represent a feasible adjunct when routine assessment and pelvic MRI fail to localize the opening. The absence of a comparator and the relatively short follow-up prevent conclusions regarding comparative accuracy, safety or recurrence reduction. Larger prospective comparative studies with long-term follow-up are required.