TRansmural hEaliNg Definition in CroHn's Disease (TRENCH 1)

Inclusion Criteria:

• ≥ 18 years of age

• Patient diagnosed with CD for more than 6 months with histological confirmationavailable in his medical record.

• Indication for MRE based on routine clinical practice validated by the treatingphysician

• Any CD treatment will be authorized, such as biologicals (infliximab, adalimumab,vedolizumab, ustekinumab...), or immunomodulators (azathioprine, 6-mercaptopurine,methotrexate...).

• The subjects sign and date a written, informed consent form and any required privacyauthorization prior to the initiation of the study.

• A subject can be enrolled into the study only if the grade of TH (assessed by theLRP) corresponding to the subject is not already fulfilled.

Exclusion Criteria:

• Pregnancy during the study

• People unable to give consent (because of their physical or mental state)

• Absence of written consent

• Ulcerative colitis or unclassified IBD

• Specific postsurgical settings: ileoanal anastomosis, ileostomy or colostomy.

• Less than 3 evaluable ileocolic segments or more than 3 resected ileocolonicsegments (not counting ileocecal valve)

• Severe obstructive symptoms

• Symptomatic intra-abdominal abscess

• Contraindication for MRI

• Isolated perianal disease without luminal location

• MRE images of poor quality, based on previously defined criteria