In this paper a CFD study of afferent loop syndrome after Billroth II gastric resection is presented. Three-dimensional CFD simulation is used in this study in order to investigate conditions at the duodenal stump after Billroth II gastric resection which may cause duodenal stump blowout. We performed virtual gastric resection using the preoperative Finite Element (FE) model based on MSCT Dicom. Three models after Billroth II gastric resection were created. CFD calculation was performed employing these models with data from literature. We calculated pressure and velocity distribution, as well as saliva and pancreatic juice and bile concentrations. After CFD simulation we had better insight into the processes within the duodenal stump after surgical intervention. This study can be useful for predictions of surgical complications.