Numerical analysis of pouch filling and emptying after laparoscopic gastric banding surgery

Previous studies have indicated that pouch volume and stoma size are two important factors related to weight loss after laparoscopic gastric banding in morbid obese patients. We hypothesized that there was association among the wall stress, pouch volume, and stoma size in a model for the filling and emptying phases of the pouch.

A numerical pouch model with variable pouch volume and stoma size was generated. Uniaxial tensile testing was performed on fundus strips from fresh pig stomach and the mass flow of filling and emptying of the pouch was simulated numerically.

There was an overall qualitative agreement on the volume change between the simulated results and the clinical recording. Increasing the pouch volume size from 22 to 105 ml caused a decrease of the maximum circumferential stress from 14.14 to 11.80 kPa and the maximum longitudinal stress from 9.87 to 6.70 kPa in the pouch wall at the same degree of filling. Decreasing the stoma diameter from 27 to 10 mm caused an increase of the maximum circumferential stress from 11.46 to 12.78 kPa and a decrease of the maximum longitudinal stress from 10.34 to 8.69 kPa.

Both the pouch volume and stoma size are important determinants of mechanical wall stress, wall strain, and pouch emptying and hence may affect satiety and weight loss. This information may be important in understanding the mechanical behavior of pouches and for the development of more advanced numerical models in the clinical management of the surgery.