Superior predictive value of transmural over endoscopic severity for colectomy risk in ulcerative colitis: a multicentre prospective cohort study

Background and Aims: Endoscopic activity is associated with an increased risk of surgery in patients with ulcerative colitis [UC]. Transmural activity, as defined by Milan Ultrasound Criteria [MUC] > 6.2, reliably detects endoscopic activity in patients with UC. The present study aimed to assess in UC patients whether transmural severity is a better predictor of colectomy as compared to endoscopy. Methods: Consecutive adult UC patients were recruited in two IBD Referral Centres and underwent colonoscopy and intestinal ultrasound in a blinded fashion. The need for colectomy was assessed at follow-up. Univariable and multivariable logistic and Cox regression analyses were performed. Receiver operating characteristic [ROC] analysis was used to compare MUC baseline values and Mayo Endoscopic Scores [MES] in predicting colectomy risk. Results: Overall, 141 patients were enrolled, and 13 underwent colectomy in the follow-up period. Both MES (hazard ratio [HR]: 3.15, 95% confidence interval [CI]: 1.18–8.37, p = 0.02) and MUC [HR: 1.48, 95% CI: 1.19–1.76, p < 0.001] were associated with colectomy risk, but only MUC was independently associated with this event on multivariable analysis [HR: 1.46, 95% CI: 1.06–2.02, p = 0.02]. MUC was the only independent variable associated with colectomy risk in patients with clinically active disease (odds ratio [OR]: 1.53 [1.03–2.27], p = 0.03). MUC demonstrated higher accuracy than MES (area under ROC curve [AUROC] 0.83, 95% CI: 0.75–0.92 vs 0.71, 95% CI: 0.62–0.80) and better performance for predicting colectomy [p = 0.02]. The optimal MUC score cut-off value for predicting colectomy, as assessed by the Youden index, was 7.7. Conclusions: A superior predictive value was found for transmural vs endoscopic severity for colectomy risk in UC patients.