Systematic Review on definitions of Intestinal Ultrasound Treatment Response and Remission in Inflammatory Bowel Disease

Intestinal ultrasound (IUS) is emerging as a valuable tool to assess treatment response in inflammatory bowel disease (IBD) clinical trials. This study details how IUS defines response and remission to evaluate treatment efficacy in IBD patients. We conducted a comprehensive search of studies from 1984 to 31 March 2024, focusing on IUS use in assessing treatment efficacy in IBD. A total of 51 studies were included: 31 on Crohn's disease (CD), 12 on ulcerative colitis (UC) and 8 on IBD. Ileocolonoscopy was used as a reference standard in 53% of studies. IUS-defined response was reported in 47% of studies, with the majority (71%) using changes in bowel wall thickness (BWT) and color Doppler signals (CDS) as key indicators. IUS-defined remission was reported in 53% of studies, primarily using normalization of BWT to less than 3 mm and CDS to grades 0 or 1 as criteria. Ultrasonographic activity scores were used in 16% of studies, including the Bowel Ultrasound Score (BUSS) in two CD studies, the International Bowel Ultrasound Segmental Activity Score (IBUS-SAS) in one CD study, the Milan Ultrasound Criteria (MUC) in one UC study The remaining four studies used unvalidated scores without clear definitions of response or remission. Assessment times varied, most commonly at weeks 8-16, 6 months, 12 months, and 24 months. This systematic review reveals significant variability in IUS definitions of response and remission in IBD, highlighting the need to standardize eligibility criteria and outcome measures for IUS in IBD clinical trials.