60% of patients with Crohn's disease will undergo surgery during their lifetime and without recurrence prevention treatment, 80% of patients will have an endoscopic recurrence within 1 year of surgery. This procedure is performed as close as possible to the gastrointestinal tract, but remaining mesenteric disease is a risk factor for recurrence. Mesentery resection has encouraging results on recurrence requiring reoperation, with a reduction of over 30% in recurrences compared with the standard technique. The study authors wish to evaluate the safety of ileocolic resection surgery involving the mesentery in patients with Crohn's disease treated with biotherapy.

The study hypothesis is that mesentery surgery is no more risky than conventional (gold standard) surgery, and reduces the 6-month endoscopic recurrence rate in patients with ileocolic Crohn's disease on biotherapy requiring ileocolic resection.

Inclusion Criteria:

• The patient must have given their free and informed consent and signed the consent form
• The patient must be a member or beneficiary of a health insurance plan
• Patient with histologically proven Crohn's disease
• Patient who has undergone ileocolic resection and whose disease site is accessible to endoscopic follow-up (first or repeat operation)
• Patient on anti-TNF α: infliximab or adalimumab (ECCO 2014 recommendation), vedolizumab, ustkinumab, or other biotherapy (e.g. risankizumab)
• Patient able to understand, write and read French

Exclusion Criteria:

• The patient is participating in an interventional study
• The patient is under safeguard of justice or state guardianship
• Medical treatment other than biotherapies including anti-TNF α (infliximab or adalimumab), vedolizumab, ustkinumab, risankinumab
• Contraindication to surgery, such as major cardiovascular comorbidities
• Pregnant, breast-feeding or parturient women