Cutting of the Intersphincteric Space for High Anal Fistula: Functional Preservation and a Predictive Model for Postoperative Anal Incontinence.

Abstract

Management of high anal fistula (HAF) remains challenging due to risks of recurrence and anal incontinence. This study was undertaken to assess the effectiveness of the cutting of the intersphincteric space (COIS) in HAF and to develop a predictive model for postoperative functional decline. A prospective single-center cohort study of 146 consecutive patients with HAF who underwent COIS at the Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine from January 2021 to July 2024, with an 18-month follow-up was conducted. COIS is a sphincter-preserving technique targeting intersphincteric space dissection to maintain anal sphincter integrity. The primary outcome was the change in anal functional status, measured by the Wexner incontinence score, at 3 months postoperatively. Secondary outcomes included recurrence rate and identification of independent predictors of functional decline via multivariate logistic regression. Significant anal functional decline occurred in 11.6% (17 of 146) of patients, with a recurrence rate of 4.8%. Sex, age, and neutrophil ratio were independent predictors of functional decline (area under the curve 0.739, 95% CI 0.645 to 0.833). A nomogram incorporating these biomarkers demonstrated excellent calibration and clinical use. Single-center design may limit generalizability; external validation in multicenter cohorts is warranted. COIS represents a functionally optimized approach for HAF, balancing radical cure and sphincter integrity. The predictive model integrating systemic biomarkers advances personalized risk assessment, guiding surgical decision-making for patients prioritizing continence. These findings underscore the importance of metabolic and inflammatory profiling in prognostication, shifting the paradigm from anatomy-driven to function-preserving strategies.