Different limb lengths in gastric bypass surgery: study protocol for a Swiss multicenter randomized controlled trial (SLIM)

BACKGROUND: Obesity and type 2 diabetes mellitus are reaching epidemic proportions. In morbidly obese patients, bariatric operations lead to sustained weight loss and relief of comorbidities in the majority of patients. Laparoscopic Roux-Y-gastric bypass (RYGB) is one of the most frequently performed operations, but it is still unknown why some patients respond better than others. Therefore, a number of variations of this operation have been introduced. Recent evidence suggests that a longer bypassed biliopancreatic limb (BPL) has the potential to be more effective compared to the standard RYGB with a shorter BPL length. This article describes the design and protocol of a randomized controlled trial comparing the outcome of a RYGB operation with a long versus short BPL. METHODS/DESIGN: The trial is designed as a multicenter, randomized, patient- and observer-blinded trial. The relevant ethics committee has approved the trial protocol. To demonstrate that long BPL RYGB is superior compared to short BPL RYGB in terms of weight loss and resolution of T2DM, the study is conducted as a superiority trial. Postoperative percent total weight loss and nutritional deficiency rate are the primary endpoints, whereas morbidity, mortality, remission of obesity-related comorbidities and quality of life are secondary endpoints. Eight hundred patients, between 18 and 65 years and with a body mass index (BMI) from 35 to 60 kg/m(2) who meet the regulatory rules for bariatric surgery in Switzerland, will be randomized. The endpoints and baseline measurements will be assessed pre-, intra-, and postoperatively. DISCUSSION: With its high number of patients and a 5-year follow-up, this study will answer questions about effectiveness and safety of long BPL RYGB and provide level I evidence for improvement of the standard RYGB. These findings might therefore potentially influence global bariatric surgery guidelines. TRIAL REGISTRATION: ClinicalTrials.gov NCT04219787. Registered on 7 January 2020. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-021-05313-6.