Transmural Assessment at Ulcerative Colitis Diagnosis: From Prognostication to Treatment Target

ABSTRACT Ulcerative colitis (UC) has traditionally been classified as a mucosal disease, but accumulating sonographic, histopathological, and surgical evidence increasingly challenges this paradigm. This Y‐ECCO Literature Review evaluates a prospective Copenhagen IBD cohort study by Madsen et al., the largest to date examining intestinal ultrasound (IUS) systematically from the time of UC diagnosis. Among 193 patients with newly diagnosed left‐sided or extensive UC, bowel wall thickness (BWT) greater than 6 mm at diagnosis independently predicted colectomy within the first 3 months (odds ratio 38, 95% CI 8–270, area under the curve 0.85), with a colectomy rate of 38% in this high‐risk group versus 1.6% in those below this threshold. Combining BWT with clinical activity scores enhanced predictive accuracy further (AUC 0.95). Transmural remission, defined as BWT ≤ 3 mm without color Doppler signal, was achieved by 59% of patients at 3 months and robustly predicted steroid‐free clinical remission at all subsequent follow‐ups (81%–87% vs. 45%–59%, p < 0.001), as well as reduced steroid requirements (6% vs. 19%, p = 0.036). These findings, contextualized against converging evidence that transmural healing outperforms endoscopic healing alone in predicting long‐term outcomes, support incorporating IUS into treat‐to‐target algorithms in UC from the moment of diagnosis.