Seo, Jung-Hee

Objective: The recent advances in computational power have enabled the use of in-silico approaches in studying physiological flows. In this study, we aim to develop a digital twin of the human stomach, StomachSim, to simulate gastric biomechanics in case of motility disorders and surgery. Methods: A physiologically realistic model of the stomach, including the antral motility, is synthesized based on in-vivo imaging data. The mixing and gastric emptying are simulated using computational fluid dynamics (CFD). Fundic accommodation, terminal antral contraction, and the phasic opening of the pyloric sphincter are incorporated into the model. The enlargement and disruption of pyloric sphincter due to pyloric intervention procedures or pyloric incompetence is also implemented. The influence of food properties (density and viscosity), motility disorders (50% reduced amplitude of antral contractions), and pyloric intervention procedures on gastric mixing, duodenogastric reflux, and solid-food trituration is investigated. The gastric emptying rate and the transpyloric pressure gradient predicted by the model were in good agreement with existing in-vivo measurements in the literature. Results: Reduced antral motility led to inefficient mixing of gastric contents and 49% lower pressure forces and 33% reduced hydrodynamic shear stresses on solid food particles. In cases with pyloric incompetence, reduced motility resulted in 66% lower duodenogastric reflux rate. When the gastric contents were of higher viscosity, the proximal stomach applied a higher pressure to achieve the same emptying rate resulting in reduced duodenogastric reflux. Higher viscosity also led to over 7 times increased shear stresses on solid food particles. Food density, on the other hand, primarily affected the transport of refluxed contents – when the gastric contents were lighter, duodenal contents entering the stomach settled along the lower antrum, and when the gastric contents were heavier, the reflux contents were transported proximally towards the esophagus. Conclusion: The digital-twin model presented in this study allows the exploration of a wide set of parameters related to gastric function. Our simulations quantify the consequences of motility disorders on gastric digestion and duodenogastric reflux. The model also reports detailed force characteristics of solid food particles undergoing trituration. StomachSim offers a novel and potentially effective modality for examining the effect of gastric conditions and gastric surgical procedures on gastric function. The authors acknowledge support from NSF award CBET 2019405. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Pyloric interventions are surgical procedures employed to increase the gastric emptying rate in gastroparesis patients. In this study, we use an in silico model to investigate the consequences of pyloric intervention on gastric flow and emptying for two phenotypes of gastroparesis: antral hypomotility and decreased gastric tone. The transpyloric pressure gradient predicted by the in silico model, based on viscous fluid flow equations, is compared against in vivo measurements. Both phenotypes exhibit a similar pre-procedural emptying rate reduction, but after pyloric surgery, antral hypomotility case with preserved gastric tone shows significant improvements in emptying rates, up to 131%, accompanied by bile reflux from the duodenum into the stomach. Conversely, severely reduced gastric tone cases exhibited a post-procedural reduction in the net emptying rate due to the relatively larger bile reflux. In cases with a combination of antral hypomotility and reduced gastric tone, post-procedural improvements were observed only when both conditions were mild. Our findings highlight the pivotal role of the relative increase in pyloric orifice diameter in determining post-operative emptying rates. The study suggests a possible explanation for the selective response of patients toward these procedures and underscores the potential of in silico modelling to generate valuable insights to inform gastric surgery.

Aim: We have developed StomachSim, an in-silico simulator that is designed to simulate the biomechanics and fluid mechanics of a wide range of gastric conditions as well as gastric surgical procedures. Here we demonstrate its use in quantifying the effects of motility disorders and pyloroplasty on the hydrolysis and emptying of a liquid meal inside the stomach. Methods: A physiologically realistic model of the stomach, including the antral motility, is synthesized based on in-vivo imaging, and the mixing and gastric emptying are simulated using computational fluid dynamics (CFD). The enzymatic biochemistry for protein hydrolysis is also implemented by incorporating the secretion of a proteolytic enzyme from the proximal stomach walls and the subsequent enzymatic reaction with the protein dissolved in the liquid meal. Using this model, we measured the effect of stomach motility and the diameter of the pyloric orifice on the retropulsive and pyloric jets, the rate of hydrolysis in different regions, and the emptying of gastric contents. Results: This study presents a proof-of-concept for the application of StomachSim in gastric disorders and surgeries. The emptying rate of our model for the healthy case agreed with the in-vivo measurements of similar caloric density liquid meals. A stomach with a 50% lower motility amplitude had a 35% lower net emptying rate and a 41% lower emptying rate of the hydrolyzed protein. Furthermore, the emptying rate showed a non-linear variation with respect to the motility of the stomach. For a simulated pyloroplasty procedure where the pyloric orifice diameter is doubled and the orifice stays open permanently, the emptying rate of the lower motility case doubled over its original value. Conclusion: StomachSim offers a novel and potentially effective modality for examining the effect of gastric conditions and gastric surgical procedures on gastric function. Our simulations show that gastroparesis and pyloroplasty not only affect the emptying rate but also alter the mixing of contents thereby changing the rate of hydrolysis. The model helped quantify the changes in the flow of contents in the antro-duodenal region for varying degrees of gastroparesis and pyloroplasty. The authors acknowledge support from NSF award CBET 2019405 and NIH award 1R21GM139073-01. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.