Published online Oct 28, 2026. doi: 10.3748/wjg.116827
Revised: March 23, 2026
Accepted: May 12, 2026
Published online: October 28, 2026
Processing time: 213 Days and 22.6 Hours
Due to the unique pathogenesis of perianal fistula in Crohn’s disease (PFCD), transmural inflammation and active proctitis are characteristic features observed on magnetic resonance imaging (MRI). These features may help predict Crohn’s disease when anal fistula is the first manifestation.
To assess the value of MRI in predicting PFCD.
In this retrospective study, 251 inpatients and 168 inpatients with anal fistula who had undergone MRI at two hospitals were included in the discovery and external validation cohorts, respectively. Images were classified based on the presence of transmural inflammation or active proctitis. A diagnostic predictive model was developed and its performance was assessed using the area under the curve, with both internal and external validations per
Of the 69 patients with PFCD in the discovery cohort, 57 had transmural inflammation or active proctitis: (1) 21 (30.4) had both features; (2) 11 (15.9) had transmural inflammation only; and (3) 25 (36.2) had active proctitis only. In contrast, among the 182 patients with cryptoglandular anal fistula, only 35 (19.2) had these features. Using transmural inflammation or active proctitis to predict PFCD yielded a sensitivity of 82.6% and a specificity of 80.8%, with an area under the curve of 0.818 (95%CI: 0.757-0.879; SE = 0.031), indicating the model’s good discriminative ability, which was confirmed in the external validation cohort.
MRI can predict PFCD and distinguish it from cryptoglandular anal fistula with good accuracy.
Core Tip: This study confirms the high value of magnetic resonance imaging (MRI) in predicting perianal fistula in Crohn’s disease (PFCD) and distinguishing it from cryptoglandular anal fistula. Transmural inflammation or active proctitis on MRI are key PFCD features, with the predictive model showing 82.6% of sensitivity and 80.8% of specificity in the discovery cohort, and even better performance in external validation. Therefore, MRI serves as a reliable non-invasive tool for early PFCD diagnosis, guiding rational treatment and helping to avoid unnecessary harm to patients.