Up to 50% of patients with Crohn’s disease (CD) develop fistulas. To explore this association, a retrospective study evaluated whether MRI could help predict perianal fistula in CD (PFCD) and distinguish it from cryptoglandular anal fistula (CAF). The study included 251 patients in the discovery cohort and 168 in the external validation cohort. In the discovery cohort, 69 patients had PFCD, of whom 57 had either transmural inflammation or active proctitis on MRI.

Among them, 21 had both features, 11 had transmural inflammation alone, and 25 had active proctitis alone. In comparison, only 35 of 182 patients with CAF had either of these MRI features. The presence of transmural inflammation or active proctitis showed good performance in predicting PFCD, with 82.6% sensitivity, 80.7% specificity, and an area under the curve (AUC) of 0.818. The model demonstrated similar performance in the…