Food Digestion in the Stomach after Bariatric Surgery: Insights from Multiphase Flow Modeling*

The geometry and contraction behavior of the stomach profoundly affect the digestion of liquid food with gastric solvent. Sleeve gastrectomy, a weight-loss surgery, reduces stomach size by 75-80%, aiding patients in consuming less food and losing weight. This study aims to investigate the impact of changes in stomach shape and contraction behavior on digestion within the stomach after a specific type of bariatric surgery – the laparoscopic sleeve gastrectomy. Based on the original model, modifications were made to reflect the post-surgical stomach. The first modification involved resecting a portion of the stomach and suturing the remaining part to form a new stomach geometry. The second modification altered the stomach's contraction pattern from bilateral to unilateral contraction. This change was made because, post-surgery, the resected side of the stomach no longer contracts. Thus, the new stomach model features a non-contracting resected side, while the remaining side retains its contraction capability. Multiphase flow simulations were conducted on this modified stomach model to study how the altered geometry and contraction behavior affect the digestion of gastric contents. These results were compared with those from the original, unmodified stomach model. The simulation results suggest that the reduced stomach volume leads to faster transport of contents from the proximal stomach to the antrum. The decreased peristaltic behavior also results in a slower mixing of gastric contents. This study demonstrates the potential of in-silico models in planning and understanding the effects of surgery.