Objective: This study assesses the prognostic role of intestinal ultrasound (IUS) in determining the disease course of ulcerative colitis (UC) in the first year after diagnosis.

Methods: A prospective, multicenter population-based inception cohort study was conducted on patients newly diagnosed with UC. Patients with left-sided or extensive UC underwent IUS assessments at diagnosis, 3 months, and 12 months, alongside symptomatic, biochemical, and endoscopic evaluations. Transmural remission was defined as bowel wall thickness ≤3 mm without color Doppler signal in all segments.

Results: From May 2021 to April 2023, 193 patients with left-sided or extensive UC were included. Inflammatory findings on IUS at diagnosis were associated with symptomatic, biochemical, and endoscopic markers of inflammation, but not with diagnostic delay. IUS-detected inflammation at diagnosis was an independent predictor for colectomy within the first 3 months, with bowel wall thickness >6 mm as the optimal cutoff (odds ratio 38, 95% confidence interval, 8-270, P < .0001). Three months after diagnosis, 59% of patients achieved transmural remission, which was associated with higher rates of steroid-free clinical remission in all subsequent follow-ups, as well as a reduced need for steroids during follow-up (6% vs. 19%, P = .036). Furthermore, transmural remission at 3 months increased the likelihood of steroid-free clinical remission, as well as transmural and complete remission, at 12 months.

Conclusions: Findings by IUS at the time of diagnosis predict early colectomy risk in UC. Our results underscore that transmural remission is a feasible treatment target in early UC, and significantly impacts the disease course.