Numerical analysis of urine flow in a stented ureter using various sizes of double J stents

The ureter is a way for urine to flow from the kidney to the bladder. A double J stent is inserted in a ureteral stenosis or occlusion due to various ureteral diseases. Here, we investigated urine flow in the stenosed ureter with various sizes of double J stents. Two ureter models (4.57 mm diameter and 5.39 mm diameter) with ureteral stenosis (0, 33, 52, 74%) were combined with four different sizes of double J stents (5, 6, 7, 8Fr) for numerical analysis. A double J stent consisted of proximal and distal coils in the ends and a shaft in the mid. There were multiple side holes in the coils and shaft. Side holes in the shaft were made in two different ways, 1cm interval with 90° angular rotation or 0.5cm interval with 90° angular rotation. Total flow rate, sum of extraluminal and luminal flow rates, in the ureters with a 5Fr double J stent was bigger than that in the ureters with the other sizes of double J stents. Total flow rate decreased with the increase in size of a stent. Although the placement of a bigger stent in the stenosed ureter seems to result in higher total flow rate, it caused lower total flow rate. In contrast, the insertion of a smaller stent resulted in higher total flow rate which was from higher extraluminal flow rate.