Intestinal Ultrasound and MRI for Monitoring Therapeutic Response in Luminal Crohn’s Disease: A Systematic Review

Background Cross-sectional imaging facilitates assessment of transmural healing in Crohn’s disease. This systematic review addresses the utility of magnetic resonance imaging (MRI) and intestinal ultrasound (IUS) in the assessment of disease activity in response to drug therapy when compared to endoscopy in patients with luminal Crohn’s disease. Methods Database searches were undertaken using predefined terms. Studies with ≥ 10 luminal Crohn’s disease patients with paired endoscopy and imaging (MRI or IUS) following treatment initiation were included. Publications were identified through searches of six bibliographic databases, all run on 24 June 2022. Records were screened on title and abstract, then full text, by two independent reviewers. Results 5760 records were identified with 24 studies meeting the inclusion criteria. Ten studies examined IUS and found good correlation between IUS and endoscopic remission (κ=0.63-0.73). Early reduction in bowel wall thickness (BWT) at 4-8 weeks predicted endoscopic response at 12-38 weeks (AUROC 0.77, OR 10.8; P=0.01). 12 studies examined MRI with the MaRIA score having high accuracy for predicting endoscopic remission (AUROC 0.97, sensitivity 93%, specificity 77%). A Simplified MaRIA score cut off of ≥1 identifies active endoscopic disease (AUROC 0.92, 95%CI 0.88-0.95, P<0.0001). Conclusion Intestinal ultrasound and magnetic resonance imaging are both reliable, non-invasive modalities for assessing transmural healing in Crohn’s disease and accurate in monitoring the response to drug therapy. These modalities can be used to monitor response to biologic induction therapy with early changes predictive of response to treatment.