Abstract
Histological remission is a key predictor of clinical outcomes and guides treatment decisions in ulcerative colitis (UC). Intestinal ultrasound (IUS) offers a promising non-invasive surrogate marker for histological activity; however, limited data exist on its correlation with validated histological indices and its predictive value for longitudinal outcomes. This study aimed to evaluate the correlation between IUS parameters, including bowel wall thickness (BWT) and Milan Ultrasound Criteria (MUC), and histological activity assessed by the Nancy Histological Index (NHI), as well as the predictive value of IUS parameters in determining clinical remission at six months. 50 of 70 planned cases were recruited and included in this interim analysis. IUS parameters were recorded for the sigmoid colon, with BWT measured as the average of two transverse and two longitudinal views, and bowel wall flow (BWF) or modified Limber score assessed on a scale of 0-3. MUC was calculated as MUC = 1.4xBWT(mm) + 2xBWF, where BWF=l if present or 0 if absent. Histological activity was defined as NHI21. Endoscopic activity was assessed using Mayo Endoscopic Score and UCEIS, and clinical activity using partial Mayo Score. Correlation analyses were performed between IUS and histological indices, with receiver operating characteristic (ROC) analyses conducted to evaluate the ability of IUS parameters to predict histological activity. Logistic regression was used to assess the association between IUS parameters and clinical remission at six months. A total of 50 patients were included, with a median age of 41 years (±14.8) and 36% female. Based on the Montreal classification, 12% had proctitis (El), 38% left-sided colitis (E2), and 50% extensive colitis (E3). Histological activity in the sigmoid demonstrated a weakly positive correlation with MUC (r=0.31; P=.032), with a trend observed for BWT (=0.27; P=.06). MUC demonstrated the greatest accuracy for predicting histological activity, with an area under the curve (AUC) of 0.72 (P=.030). A cutoff value of MUC>3.6 achieved a sensitivity of 80% and specificity of 63%. This cutoff also showed a trend toward predicting clinical remission at six months (odds ratio: 0.33; 95% CI: 0.09-1.19; P=.090). In comparison, BWT alone was less accurate, with an AUC of 0.69 (P=.065) for predicting histological activity and a cutoff value of BWT>2.2mm demonstrating a sensitivity of 80% and specificity of 53%, without a significant association with clinical remission at 6 months (P=.244). IUS demonstrate potential as a non-invasive marker of histological activity in UC and a predictor of clinical outcomes. These findings highlight the utility of IUS for monitoring UC and supporting point-of-care decision-making, reducing the reliance on colonoscopy. Further studies are needed to validate these findings and refine diagnostic thresholds.