H. A. Frohman1,2, P. G. Rychahou1,2, J. Li2, B. M. Evers1,2 1University Of Kentucky,Department Of Surgery,Lexington, KY, USA 2University Of Kentucky,Markey Cancer Center,Lexington, KY, USA
Introduction: Roux-en-Y gastric bypass surgery (RYGB) has been shown to improve comorbidities such as diabetes and hypertension and lower the risk of obesity-related cancers. To better understand the physiologic and genetic influences of RYGB and sleeve gastrectomy (SG), a model is needed that can be extended to genetically engineered transgenic species. However, given the complexity of these procedures, few researchers have successfully implemented these techniques beyond larger rodent models. Therefore, the purpose of our current study was to develop a technically feasible and reproducible small animal model for RYGB and SG.
Methods: Swiss-Webster mice were fed high-fat diet for 20 wks to induce morbid obesity. All mice received ciprofloxacin preoperatively. An injectable analgesic and subcutaneous fluids were provided following induction of anesthesia with inhaled Isoflurane. Sham surgeries consisted of enterotomies and gastrotomy followed by primary repair without resection or rerouting.
Results: Pre- and postoperative techniques that failed included: fasting mice for 12 h prior to operation, housing mice individually, use of bedding within 7 d of operation. Surgical techniques that failed included: end-to-side anastomosis of the jejunojejunostomy, running suture along the full length of the anastomoses, and creation of a gastric pouch less than 40% of stomach volume for RYGB surgery.
The pre- and postoperative techniques that improved mouse survival included conversion to liquid diet 72 h prior to surgery and resuming liquid diet for 7 d post-op without fasting, wire bottom cages, and housing mice with other mice – one of which received no surgery.
The surgical techniques that were successful for RYGB surgery consisted of intraoperative use of a far infrared heat source to increase deep tissue temperature, side-to-side functional end-to-side anastomoses, and running suture along the posterior wall of the anastomoses followed by approximation of the anterior walls with interrupted sutures. Furthermore, the surgical technique that resulted in the fewest SG complications was closure of the stomach in two layers, with the outer layer being an imbrication of gastric serosa.
Survival after incorporation of aforementioned techniques was 100% in the SG group, 67% in the sham-RYGB group, and 30% in the RYGB group at 1 month after surgery. Only 22% of RYGB mortality was attributed to leak, obstruction, or stricture. The remaining RYGB mortality was related to stress, dumping, or malnutrition.
Conclusion: Bariatric surgery in a mouse model is technically challenging but feasible. Much of the survival challenge for this surgery model is related to pre and post-operative mouse care, which is to be expected given their small stature and poor response to stress. Utilization of the surgical techniques described will produce similar results for researchers aiming to study effects of bariatric surgery.