Numerical Simulation of Peristaltic Urine Flow in a Stented Ureter

The capacity of ureteral stents to enhance the conveyance of urine from kidney to bladder is the critical function for patients that require them. The flow path in and around the stent is not a trivial one, particularly if some elements of peristalsis are present in the ureter. This paper details a numerical flow simulation for an axially symmetric stented ureter segment. The flow of urine through a stented, elastically-modeled ureter was considered under varying pressure gradients, bore (lumen) obstructions, and peristaltic deflections (waves). Peristaltic waves are combined with the pressure gradient developed between the kidney and bladder to provide a more accurate representation of the complex flow mechanics found within the ureter. Although it is recognized that peristalsis ceases or diminishes greatly after prolonged presence of a stent, in the time frame that it is active, detrimental consequences like reflux may occur. Several relationships from varying control parameters are determined to predict the onset of reflux as flow conditions within the ureter change. It was determined that occurrence of reflux is more likely as the peristaltic deflection or the obstruction of the stent bore increases. The threat of reflux is low if the pressure gradient between the kidney and bladder remains large. These simulations provide insight into the fluid behaviour within a stented ureter that could lead to optimized stent designs and reduce the possibility of reflux, infection, and discomfort.