Investigation of Fluid Flow Through the Ureteral Canal with A Porous Media Approach in the Ureteral Stone Reduction Process

Abstract

This study includes the examination of the stone removal process by computational fluid dynamics analysis in the kidney and ureteral canal, which is modeled as the fluid evacuation channel for the urine flow. SolidWorks 2020 R2 commercial software was used for three-dimensional modeling and Flow Simulation plugin for flow simulation analysis. The kidney with the size of 12x6x6cm and in addition to this, the ureteral canal with the largest internal diameter of 20 mm (at the kidney outlet) and the smallest diameter of 5 mm (at the canal outlet) were modeled. Pressure distribution in the presence of flow was determined in case of stone stuck in the middle part of the ureteral canal. To identify the partially occluded region allowing flow, the kidney stone region was defined as a porous medium for analysis. Four different conditions (between 0.90 and 0.99) for permeability in this region were included in the analysis to represent stone size and structure. The change in pressure-velocity distribution and its effect in the kidney area were seen at 5 different entry speeds. The effect of different permeability conditions on the pressure difference was shown graphically. The findings showed the presence of high pressure (peak 1850 mmH2O) throughout the flow volume at narrow passages and low permeability conditions, as expected. At 90% permeability, the maximum local velocity in the blockage zone was found to be 4.5 m/s and this value tends to decrease with increasing permeability. It was predicted that the pressure-velocity relationship along the flow can provide information on treatment and intervention, depending on the stone and canal structure whose properties are predetermined. It was concluded that a preliminary idea could be formed about the extent of pain due to high pressure, especially for the stone dropping process, which does not cause complete obstruction in the canal and is defined as a porous medium in this analysis.