The EXCEED project aims to study the role of the mesentery in disease recurrence in Crohn's disease (CD), as evidence suggests that including the mesentery when doing ileocecal resections can significantly reduce recurrence rates. The EXCEED study is a blinded randomised clinical trial with 204 participants having ileocecal Crohn's disease requiring resection. Participants will undergo either "standard" mesocolic sparing resection or extended mesocolic resection to assess its impact on reducing recurrence at the anastomotic site. The primary endpoint is endoscopic recurrence 12 months postoperatively.

Additionally, the study aims to evaluate the efficacy of different surveillance modalities in detecting anastomotic site recurrence. These examinations will be conducted pre- and postoperatively for a cohort of 20 participants.

Through this study, we seek to understand the mesentery's role in Crohn's disease recurrence and identify effective non-invasive methods for postoperative monitoring.

Surgical Procedure and Perioperative Care Laparoscopic approach with a minimum 5 cm disease-free bowel on each side. Standard stapled side-to-side isoperistaltic anastomoses. Extended mesenteric excision involves resection of inflamed mesentery up to the level of visible inflammation.

Both treatment groups will receive standard postoperative care according to the standards of the hospital treating the participant.

Postoperative Follow-up Postoperative follow-up at 6 and 12 months. This consist of an ileo-colonoscopy, chart review and questionnaires. The early follow-up at 6 months aims to detect early recurrence, enabling early medical treatment or other intervention. The 12-month follow-up will be the primary endpoint to determine recurrence. Long-term outcomes will be assessed through a chart review after 3 and 5 years, documenting reoperations, clinical symptoms, pharmacological use, and other complications.

Postoperative Medicinal Use Postoperative medical prophylaxis assessment isn't explicitly detailed in the current protocol, though it will be acknowledged. Analysis will stratify participants based on pre- and post-operative biological/non-biological treatment. The treating physician will determine postoperative medical therapy, typically maintaining pre-operative medication.

Postoperative Endoscopy Endoscopy will be regarded as the golden standard for the detection of disease recurrence. The endoscopies, including bowel preparation and possible sedation, will be preformed in accordance with local guidelines at each hospital. At least three biopsies will be taken from the ileum (5 cm proximal to the anastomosis), anastomosis, and colon (5 cm below the anastomosis). A short video of each endoscopy will be saved for validation purposes. Lesions found during the endoscopy will be classified using the modified Rutgeerts score[7].

Patient-Reported Outcome During the preoperative workup (baseline), the participant will be asked to complete 2 questionnaires (5Q-5D-5L and SIBDQ). Postoperatively, the participant will be asked to complete the same questionnaires at 6 and 12 months.

Statistical analysis plan Outcome Analysis The investigators plan to conduct a chi-square or Fisher's exact test to compare the proportion of participants with endoscopic recurrence between the intervention and control groups.

The investigators will utilize logistic regression to adjust for potential confounding variables if needed.

Demographics The Investigators will use means and standard deviations (or medians and interquartile ranges) for continuous variables. For categorical variables, frequencies and percentages will be presented and demographic characteristics between intervention and control groups will be compared.

Inclusion Criteria

• Patients above the age of 18 scheduled for ileocecal resection due to Crohn's disease.
• Relevant endoscopy and imaging within the last 6 months.
• Diagnosis of "simple" ileocecal Crohn's disease (limited to ileocecal disease with a maximum of 40 cm of affected ileum).

Exclusion Criteria

• Previous ileocecal resection.
• Inability to understand Danish or another Nordic language.
• Inability to comprehend the purpose and design of the project.
• Pregnancy or lactation.

The principal investigators are committed to communicating the results, negative, positive, or inconclusive results, at local, national and international scientific meetings. The findings will be published in well-established, international peer-reviewed open access journals. After end of study, de-identified patient data will be uploaded to an open repository for further use.

After study completion.

Available to all upon request

This randomized controlled trial will incorporate blinding procedures, with the understanding that due to the nature of this interventional surgical study, the operating surgeon cannot be blinded. However, rigorous measures will be implemented to ensure blinding of both patients and all other participants involved in patient treatment. The description of the surgery within the patient chart will follow a standardized format, with the exception of the resection details. Where the two treatment methods diverge, a predefined, standardized text referencing the study will be inserted.