Comparing Three Modalities (Trans Abdominal, Trans-perineal and Endoscopic Ultrasound) of Ultrasonography for Rectal Imaging in Ulcerative Colitis: The TRINITY Study

This study is designed to assess the correlation of rectal wall thickness and vascularity measurements obtained through trans-abdominal ultrasound (TAS), trans-perineal ultrasound (TPUS), and endoscopic ultrasound (EUS) in adult patients with ulcerative colitis (UC). The primary goal is to determine how well rectal total wall thickness measured via TPUS correlates with EUS findings. Secondary objectives include comparing rectal wall thickness and vascularity measured by TAS, TPUS, and EUS with endoscopic activity, histologic activity, and fecal calprotectin (FCP) levels. Additionally, the study aims to evaluate changes in patient management resulting from additional investigations, such as sigmoidoscopy and EUS, over the standard TAS and TPUS procedures. UC patients attending an inflammatory bowel disease (IBD) clinic will undergo a clinical assessment using the Simple Clinical Colitis Activity Index (SCCAI), followed by baseline TAS and TPUS, both performed as point-of-care tests. If deemed clinically necessary, patients will also undergo sigmoidoscopy and EUS during the same visit, with rectal wall thickness and vascularity measured across different rectal sections and correlated with histologic inflammation assessed via biopsy and measured by the Nancy histologic index. The study will also explore correlations with FCP levels where data are available. This cross-sectional study includes a follow-up period until biopsy results are obtained, with an estimated recruitment duration of 6-12 months and a target sample size of 50 patients.