Computational Multiphysics Modeling of the Postprandial Human Stomach
Health problems related to the mechanics of the stomach (gastric mechanics) are among the most important causes of morbidity in industrialized countries. For example, around 10% - 20% of the population in Western countries suffers from gastro-esophageal reflux disease (GERD), which results from a mismatch between the intragastric pressure and the closing pressure of the esophagus. Around 10% - 45% of the general population suffers from dyspepsia, that is, difficult digestion, which is often linked to the motility of the stomach. Altogether, healthcare costs related to the stomach and gastrointestinal tract are roughly comparable to the ones associated with cardiovascular diseases. Interestingly, this tremendous importance of the stomach is not at all reflected by current research efforts. In the program of the 7th World Congress of Biomechanics in 2014 with more than 4000 presentations common cardiovascular keywords (cardio, cardiac, vascular, heart, coronary, aneurysm, artery, arteries, arterial, athero/arteriosclerotic) are found 424 times, keywords related to the stomach (stomach, gastric, oesophagus, esophageal, esophagus) only 3 times. Three-dimensional computational fluid mechanics was first applied to arteries around 1990, to the stomach only in 2007. Computational models incorporating fluid-structure interactions were developed for the vasculature already in the mid-1990s but no such model has been proposed for the stomach so far. In short, computational modeling of the stomach lags around 20 years behind modeling of the cardiovascular system. This project aims at closing this important gap in biomechanical research by developing the first computational multi-physics model of the human stomach. This major objective will be achieved in four steps: first, tissue patches from the human stomach will be harvested in the hospital and subjected to biaxial mechanical testing in order to determine the mechanical constitutive properties of human gastric tissue; second, data about the dynamic deformation of the human stomach during digestion and emptying will be collected by magnetic resonance imaging (MRI); third, on the basis of these mechanical and imaging data, a computational multiphysics model of the human stomach will be developed that incorporates the mechanics and electrophysiology of the gastric wall, the fluid mechanics of the digesta and also fluid-structure interactions; fourth, using this computational model in-silico studies will be performed that will enable for the first time a mechanistic understanding of the complex interplay between the different physiological processes and parameters in the stomach and the way how they affect digestion of food. The computational model developed in this project can be expected to provide a valuable basis for future research projects examining the link between gastric mechanics and disorders and pathologies like dyspepsia, gastro-esophageal reflux disease, or morbid obesity.