Diagnostic Concordance of MR Enterography and Ultrasound for Treatment Response Assessment in Crohn's Disease (MANTRA)

Imaging, typically with MR enterography (MRE) and/or Intestinal Ultrasound (IUS), is central in the follow up of Crohn's disease patients to assess treatment response to powerful immunosuppressive therapy. Practice varies widely on which imaging modality is selected and/or available and if they are used in isolation or interchangeably. There is currently no set guidance and practice varies widely. We know that both MRE and IUS are accurate for diagnosing and staging Crohn's disease, although patients generally prefer IUS if it is of comparable accuracy. We however do not understand if MRE and IUS can be used interchangeably for treatment response assessment. Such uncertainty can impede patients and clinical teams in making informed management decisions. Currently, IUS provision is sparse with no formal training programme, leading to a heavy bias for MRE. This approach is more costly, less tolerable to patients, adds pressure to already overloaded MRI workflows, and less environmentally sustainable. The current study may support the drive for comprehensive provision of both MRE and IUS services and training. Currently, the literature is very limited and largely comprised of small single centre studies (most less than 50 patients), using inconsistent imaging definitions of treatment response, highly varied reference standards and differing follow up intervals. There are several MRE and IUS scores for objective disease assessment which remain to be fully validated for response and their respective agreement is not fully understood. Ultimately, a major outstanding research question is not if investigators should use MRE or IUS, but rather, when investigators should use them in the management of individual patients. Accordingly, the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and the James Lind Alliance/Crohn's \& Colitis UK identify the current study topic as a key research priority. The proposed prospective study will be the largest to date to investigate the accuracy of MRE and IUS for classification of treatment response against an expert consensus panel, their agreement in response assessment.