Internal hernias (IH) are a common complication following laparoscopic Roux-en-Y gastric bypass (LRYGB). The closure of the mesenteric defect (MD) is widely accepted as a measure to prevent IH. However, long-term efficacy of initial MD closure is unknown. The aim of this study is to investigate the risk of reopening of the intermesenteric and Petersen space after closure with non- absorbable suture during index RYGB. The secondary objective was to determine any risk factors associated with the reopening of the MD.

This is a retrospective analysis of all re-operations following primary LRYGB with complete closure of MD performed between 2010 and 2018. Data of all consecutive patients who underwent elective or emergency re-operations after proximal LRYGB was reviewed.

A total of 207 patients underwent a reoperation during the study period. The status of the MD was recorded in 162 patients, who were therefore included in the study. The median time between LRYGB and re-operation was 17 months (IQR 10.0 -30.5). The indications for the re-operations were as follows: gallstone disease (n= 48, 29.6%), recurrent abdominal pain (73, 45.1%), weight regain or insufficient weight loss (n=21, 13.0%), small bowel obstruction (n=14, 8.6%), symptomatic hernia (n=4, 2.5%), marginal ulcer (n=1, 0.6%), pouch fistula (n=1, 0.6%). At the time of re-operation, 35 patients (21.6%) and 28 patients (17.3%) had a partially open and totally open Petersen space, respectively. A partially open and a totally open intermesenteric defect was found in 33 patients (20.4%) and 4 patients (2.5%), respectively. Both MD were closed in 83 patients (51.2%), thus 79 patients (48.8%) presented at least one open MD. Preoperative BMI less than 40 kg/m2 at the time of LRYGB was associated with a higher risk of developing an open mesenteric defect at the time of reoperation (33 patients [41.8%] at the group of patients with at least one open MD vs 22 patients [26.5%] at the group of patients presenting both MD closed, OR 1.99, 95% CI 1.02- 3.81; P=0.047).

Primary closure of Petersen`s space and intermesenteric defect during LRYGB reduces by half the risk of an open MD. Since reopening of MD can still occur in almost half of the patients, a careful observation of the state of both MD during re-operation, regardless of their indication, is strongly recommended.