Currently, the plastic and silastic stents used by urologists around the world cause many inconveniences due to the discomfort the patients experience during its time inside the ureter tract. With the stents being elastic and moving inside the ureter, the subject will encounter discomfort and pain from the deformation of the stent that translates into a reaction force that the ureter walls must compensate. This stent is installed in order to prevent the ureter from closing after the new kidney has been sutured to the patient’s ureter. Urine would build up in the ureter and rupture the sutures placed by the medical professionals if it were not for the stent enabling the flow to be normalized. The stent is removed a few weeks later after the healing process and once the urine flow has been completely normalized.These ureter stents have differing lengths depending on the patient and have an annular cross section to allow for urine to also flow through it thanks to the side holes that allow for the urine to enter it and make its way to the bladder. Ureter stents have not received much refinement in their design in the latest years, due to which a deeper look into the physics that happen inside of the ureter with its presence might be important to find potential improvements. In the majority of kidney transplant procedures, the old kidney is left inside the patient and the new one is positioned lower in the patient’s body, closer to the urinary bladder which requires a reduction in the length of the attached ureter. This change in length requires its own flow study instead of the ones that have been performed on full-length ureters.Due to the extent of our study being outside fluid dynamics and more on how the fluid flow will deform the ureter walls and inserted stent, a fluid-structure interaction (FSI) simulation must be performed. This study will adopt COMSOL Multiphysics due to its potential to combine various physics such as FSI. The purpose of the simulation is to numerically explore the laminar flow profile inside the ureter to verify the stent’s design using the results obtained from the simulation. Considering the elastic behavior of the stent and the ureter walls, a two-way FSI simulation will be performed using COMSOL Multiphysics to study how the elastic materials will deform and how that deformation will affect the flow behavior, making the fluid and elastic deformation simulations fully coupled. The material properties of the solid will be gathered from various studies and were given isotropic properties and the flow is pressure-driven defined as laminar. Three stent models with side holes along their length will be studied to figure out the relationship between wall reaction forces, flow rate and number of holes along the stent.It is hoped that this study will present clear results that can help increase the interest in improving the stents in kidney transplant procedures, as well as optimizing the stents’ design to further ease the inconvenience on the patients that require a ureteral stent.

Numerical Study of Fully Coupled Fluid-Structure Interaction of Stented Ureter by Varying the Stent Side-Holes

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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