Mesentery Guided Bowel Resection Margin Versus Traditional Margin in Reducing Early Endoscopic Recurrence Rate After Ileocolic Resection in Patients With Crohn 's Disease:a Prospective, Multicenter, Randomized Controlled Clinical Trial

Current Status of the Study Current Status of the Study While treatment methods for Crohn's disease (CD) have made significant advancements, there is still a 50% requirement for surgical intervention within 10 years of diagnosis (1). The most common surgical procedures include ileocecal or terminal ileal resection. However, post-surgery, the risk of recurrence remains high, with 35% to 85% of patients experiencing endoscopic recurrence within one year (2, 4), and clinical recurrence occurring in 10% to 38% of patients within one year, leading to a need for reoperation in 30% of patients within five years (2, 3). Several studies have demonstrated that early endoscopic recurrence at six months post-surgery can effectively predict long-term treatment outcomes and guide subsequent medication choices (5).

Therefore, reducing early endoscopic anastomotic recurrence post-surgery has been a focus of CD research. The quality of surgical procedures significantly impacts this outcome. Previous research has identified risk factors for post-surgical recurrence, including smoking history, previous bowel resections, penetrating disease, extensive involvement, and concomitant perianal disease (6-8). However, these are non-modifiable patient-related factors. Within the scope of what physicians can control, proactive preventive treatment approaches adopted by gastroenterologists have been shown to reduce endoscopic recurrence rates to some extent. Nevertheless, the role and responsibilities of surgeons in this regard have not been clearly defined, and thus, there is a lack of standardized surgical strategies to reduce early endoscopic recurrence.（11） Intestinal mesentery abnormal proliferation and wrapping around the mesenteric margin is a characteristic pathological feature of Crohn's disease (CD). Recent studies have shown that mesenteric fat plays a crucial role in the development of CD (13, 14). The applicant's research team has also discovered the presence of bacteria displaced from the intestines within the mesentery, which can stimulate the proliferation of fat cells (15). Our preliminary retrospective data (pending submission) also suggests that if the mesenteric-guided margin, corresponding to the border of mesenteric abnormality, is used as the resection margin, even though an average of 10cm more intestine is removed, the postoperative endoscopic recurrence rate and clinical recurrence rate are significantly better than those of patients with the traditional limited 2cm margin (as described in the research foundation). However, there is currently no prospective randomized controlled study comparing these two margin strategies. Therefore, investigators plan to conduct a prospective multicenter randomized controlled study for patients with ileocolonic CD who undergo primary anastomosis without residual disease, comparing the postoperative endoscopic recurrence rates between mesenteric-guided margins and traditional 2cm margins, and conducting related mechanistic research to establish a high-level evidence for surgical margins that can reduce postoperative endoscopic recurrence in CD.

The significance of this research lies in addressing the issue of high endoscopic recurrence rates following surgery for Crohn's disease (CD), for which there is currently no established surgical solution. This study employs an innovative approach by using the mesenteric fat boundary as guidance for surgical resection margins, making it a novel contribution to both national and international research.

Building upon prior preliminary research, our research team aims to determine, through a prospective multicenter study, whether the use of mesentery-guided resection margins can reduce the endoscopic recurrence rate, while also exploring potential underlying mechanisms. The successful implementation of this project can provide high-level evidence for the correct selection of surgical margins in CD, fostering the development of personalized and precision surgical approaches in the treatment of CD in China, offering substantial clinical application and practical guidance.The ultimate goal of this study is to improve the long-term prognosis of CD patients and enhance their postoperative .