Abstract： Objective To investigate the perioperative impact of closure of mesenteric fissure in laparoscopic right hemicolectomy.Methods The prospective randomized controlled trial was conducted.The clinical data of 320 patients who underwent laparoscopic right hemicolectomy in 11 medical centers,including The First Affiliated Hospital of China Medical University et al,from November 2022 to August 2023 were selected.Based on block randomization,patients were alloca-ted into the mesenteric fissure non-closure group and the mesenteric fissure closure group.Observa-tion indicators:(1)grouping of the enrolled patients;(2)intraoperative conditions;(3)postopera-tive conditions.Measurement data with skewed distribution were represented as M(Q1,Q3)and com-parison between groups was conducted using the Mann-Whitney U test.Count data were represen-ted as absolute numbers or percentages,and comparison between groups was conducted using the chi-square test or Fisher's exact probability.Comparison of ordinal data was conducted using the rank sum test.Comparison of visual analog scores was analyzed using generalized estimating equations.Results(1)Grouping of the enrolled patients.A total of 320 patients with colon cancer were screened for eligibility,including 156 males and 164 females,aged 68(59,73)years.All the 320 patients were allocated into the mesenteric fissure non-closure group with 164 cases and the mesenteric fissure closure group with 156 cases.There was no significant difference in the age,body mass index,American Society of Anesthesiologist score,maximum tumor diameter,anastomosis location,anastomosis method,surgical approach,range of lymph node dissection,tumor staging between the two groups(P＞0.05)and there was a significant difference in the sex between them(P＜0.05).(2)Intraoperative conditions.There was no significant difference between the mesenteric fissure closure group and the mesenteric fissure non-closure group in the volume of intraoperative blood loss,operation time,conversion to laparotomy,intraoperative complication(P＞0.05).Three patients in the mesenteric fissure non-closure group were converted to laparotomy.One patient in the mesenteric fissure closure group was converted to laparotomy,and 2 cases with intraoperative complication were mesenteric hematoma.(3)Postoperative conditions.There was no significant difference between the mesenteric fissure non-closure group and the mesenteric fissure closure group in the overall postoperative complications(x2=0.28,P＞0.05).There was no significant difference in the occurrence of postoperative intestinal obstruction,abdominal distension,ascites,pleural effusion,gastric paralysis,anastomotic bleeding,anastomotic leakage,or surgical wound infection between the two groups(P＞0.05).There was no significant difference between the two groups in the reoperation,postoperative gastric tube replacement.There was no significant differ-ence in time to postoperative first flatus,time to postoperative initial liquid food intake,time to post-operative resumption of bowel movements,duration of postoperative hospital stay,total hospital expenses between the two groups(Z=-0.01,0.43,1.04,-0.54,-0.36,P＞0.05).One patient in the mesenteric fissure non-closure group received reoperation.No perioperative internal hernia or death occurred in either group.The visual analog score decreased with time in both groups.There was no significant difference in the visual analog score between the mesenteric fissure closure group and the mesenteric fissure non-closure group[β=-0.20(-0.53,0.13),P＞0.05].Conclusion Compared with closure of mesenteric fissure,non-closure of mesenteric fissure during laparoscopic right hemi-colectomy dose not increase perioperative complications or postoperative management risk.