This single-centre prospective cross-sectional study (n=59 UC patients, Jan–Sep 2023) evaluated whether layer-specific intestinal ultrasound (IUS) parameters — bowel wall thickness (BWT) by layer, colour Doppler signal (CDS) — in the sigmoid colon and rectum were associated with bowel urgency (BU), defined by the SCCAI urgency subscore, compared to endoscopic activity (Mayo Endoscopic Subscore) and biomarkers (CRP, LRG, faecal calprotectin).
56% of patients (33/59) reported BU. Sigmoid submucosal thickness (AUC 0.77) outperformed mucosal thickness (AUC 0.62, p<0.05) in discriminating BU. After adjusting for endoscopic severity, sigmoid submucosal (OR 33.43, 95% CI 2.04–548.37, p<0.01) and muscularis propria (OR 11.05, 95% CI 1.19–102.96, p=0.03) thickness remained independently associated with BU, while mucosal thickness did not (p=0.97). Faecal calprotectin was not significantly different between groups (p=0.48).
- Small sample (n=59) limits subgroup analyses and precision of effect estimates, with wide confidence intervals in regression models. - Exploratory multi-segment and multi-layer analyses were performed without correction for multiple comparisons. - Inter-rater agreement for sigmoid submucosal thickness was assessed on dichotomised (not continuous) measurements, and technical demands of layer-specific IUS may limit generalisability.
In UC patients with persistent bowel urgency despite minimal endoscopic activity, IUS assessment of sigmoid submucosal and muscularis propria thickness may reveal deeper bowel wall inflammation not captured by endoscopy. Consider IUS as a complementary tool when symptoms and endoscopy are discordant.
