The main objective of this pilot study is to show feasibility to collect peri-operative and postoperative clinical data of the study group of gastric bypass without cholecystectomy compared with the control group of gastric bypass with cholecystectomy. Our hypothesis is that the approach without cholecystectomy would be superior in terms of a decrease of perioperative adverse events and postoperative complications, as well as lenght of operation, lenght of hospital stay, overall costs with a very low risk of biliary complication in the follow up. These findings could be helpful to build a baseline for a future randomized controlled multicenter study allowing significance of these results and help orientate surgeons towards best surgical care of the gallbladder with confirmed absence of stones in the obese patient undergoing gastric bypass.

We suggest performing a prospective randomized pilot trial comparing RYGB without concomitant cholecystectomy with RYGB with concomitant cholecystectomy for patients with absence of gallstones in preoperative ultrasound. Patients with ultrasonographically confirmed gallstones in the gallbladder undergo concomitant cholecystectomy at time of RYGB and are excluded from the study.Patients who meet the inclusion criteria will be randomized according to a randomization list generated by the CRC of the University Hospital of Geneva. The randomization envelops will be opened by the study staff at the appropriate time prior to the scheduling of gastric bypass after subject selection. The randomization assignment insert will contain information specifying whether the cholecystectomy will be performed or not during gastric bypass procedure.

A total of 90 consecutive obese patients attending the Unit of Visceral Surgery of the University Hospital of Geneva who meet the criteria for bariatric surgery and where the preoperative ultrasound confirms absence of gallstones will be recruited for the study.

A prospective open randomized pilot study design will be used. At 6 follow-up visits (at discharge, 1 ,3 ,6 ,12 and 18 months post-surgery), patients will be evaluated.

This study will be conducted in compliance with the protocol, the current version of the Declaration of Helsinki, the ICH-GCP or ISO EN 14155 as wella s all national legal and regulatory requirements, the LPth (Loi sur les produits thérapeutiques 812.21) and the OClin (Ordonnance sur les essais cliniques des produits thérapeutiques 812.214.2).

Description of surgical technique One optical trocar, three 12 mm trocars and one 5 mm trocar are placed. No additional trocar has to be placed for concomitant cholecystectomy. The intervention will start with the cholecystectomy laparoscopically. A small gastric pouch (around 20-30 cc) is created using blue cartridge staplers. A standard robotic RYGB with a 75 cm biliary limb and a 150 cm antecolic alimentary limb is performed. A hand-sewn gastrojejunal and jejunojejunal anastomois are performed, using a single layer running suture of Vicryl 2.0.

Data Collection:

Pre-Operative demographic data and other variables will be collected at baseline and at some of the 6 follow-up points (at discharge, 1,3,6,12,18 months):

Ultrasound, Patient Demographics and pre-Operative History will be collected, including: Gender, age on admission for operation, BMI, Height, Weight, ASA score, history of abdominal surgery, co- morbidities (Type 2 diabetes requiring Insulin or oral medication), Hypertension requiring medication, Coronary heart disease, including history of myocardial infarction, angina pectoris, coronary artery surgery Pulmonary comorbidities including history of pulmonary embolism, Sleep Apnea Tobacco use, Medication used by patient, Systolic and diastolic blood pressure, heart rate, Fasting plasma glucose, HbA1c, laboratory findings, QOL using the EQ-5D-5L questionnaire

Intra-Operative Assessment: Intra-Operative data such as complications (organ lesion, bleeding, conversion), operative time, docking times, estimated blood loss will be collected

Post-Operative Assessment: From surgery to discharge, the following patient information will be collected: complications according to Clavien/Dindo Classification system, re- operation, re-admission, length of hospital stay

Our hypothesis is that the approach without cholecystectomy would be superior in terms of a decrease of perioperative adverse events and postoperative complications, as well as lenght of operation, lenght of hospital stay, overall costs with a very low risk of biliary complication in the follow up.

Inclusion Criteria:

• Patients must meet the criteria of the Swiss society for the study of morbid obesity (SMOB) to undergo gastric bypass (19):

  • BMI ≥ 35 kg/m2
  • Having followed a 2 year adequate program of weight loss without success or a 1 year program in case of "superobesity" (BMI ≥ 50 kg/m2)
  • Consent to multidisciplinary follow up for 5 years

• Preoperative ultrasound without presence of gallstones or polyps

• Age ≥ 18 years

Exclusion Criteria:

• Patients which have a contra-indication for gastric bypass according to the criteria of the Swiss society for the study of morbid obesity (SMOB) to undergo gastric bypass (19):

  • Pregnancy
  • Kidney failure (creatinine ≥ 300mmol/l, GFR < 30ml/min) without dialysis
  • Cirrhosis Child B/C
  • Ulcerative Colitis
  • Pulmonary embolism or deep venous thrombosis during the last 6 months
  • Psychiatric contra indications
  • Drug abuse (alcohol, cannabis, opioids) during the last 6 months

• Presence of gallstones on preoperative Ultrasound (which will require concomitant cholecystectomy)

• Patients with clinical diagnosis of cholecystitis defined as right upper quadrant abdominal pain, radiological signs of cholecystits and laboratory signs of infection or gallstone migration, defined as right upper quadrant and abnormal liver function tests (any increase in AST, ALT, alkaline Phosphatase, GGT and/or bilirubin).

• Previous bariatric surgery other than gastric banding

• Open bypass procedure

• Medical conditions preventing informed consent

Preoperative routine work-up includes a physical examination, vital parameters, laboratory analyses (hematology, chemistry and HbA1c), sleep apnea evaluation with Polygraphia, abdominal ultrasound, endoscopy of the stomach, pulmonary function, preoperative anesthesia consultation and psychological evaluation.

The results of these routine tests will be used to assess the patients'eligiibility to participate to the proposed pilot study.