Numerical Analysis of Urine Flow with Multiple Sizes of Double-J Stents

Abstract

This study investigated which sizes of double-J stents are more effective in achieving an acceptable urine flow through stenotic and stented ureters. Sixty four computational fluid dynamics models of the combinations of two different gauge ureters (4.57 mm and 5.39 mm in diameter) with four different levels of ureteral and four different sizes of double-J stents were developed for the numerical analysis of urine flow in the ureter. Luminal, extraluminal, and total flow rates along the ureter were measured, and the flow patterns around the ports and side holes were investigated. For the 4.57-mm ureter, the total flow rate for each gauge of stent was 23–63 mL/h (5 Fr), 20–47 mL/h (6 Fr), 17–35 mL/h (7 Fr), and 16–26 mL/h (8 Fr) and for the 5.39-mm ureter, the total flow rate for each gauge of stent was 43–147 mL/h (5 Fr), 36–116 mL/h (6 Fr), 29–92 mL/h (7 Fr), and 26–71 mL/h (8 Fr). With a 74% stenosis, all stents allowed a low flow rate, and the differences in flow rates between the stents were small. At the other levels of stenosis, 5 Fr stents allowed greater flow rates than the 8 Fr stents. The luminal flow rate increased just before the area of stenosis and decreased after the stenosis because of the increase and decrease in the luminal flow through the side holes before and after the stenosis. Therefore, a larger double-J stent is not favorable in achieving an acceptable urine flow through the stenotic and stented ureters. The results in this study could not be necessarily correlated with clinical situation because peristalsis, viscosity of the urine and real format of the ureter were not considered in our model. In vivo experiments are necessary for confirmation of our findings. Double J stents are commonly used in the ureteral stenosis or occlusion, especially due to ureter stones which obstruct the flow of urine. Clinicians choose the size of double J stent on the basis of their clinical experience. Here, we tried to know which sizes of double J stents are better for sufficient urine flow. According to various documents that try to determine the optimal shape of double J stents to increase the urine flow through the ureter, mostly bigger stent is recommended to occur maximum urine flow. However, in case of ureter with stenosis or occlusion, the right size of the double J stent may vary depending on the degree of stenosis in the ureter. To find appropriate stent size for the ureter with stenosis, computational fluid dynamics was conducted. This study shows that smaller diameter stents are more appropriate than larger diameter stents depending on the situation.

The accumulation of particles in ureteric stents is mediated by flow dynamics: Full-scale computational and experimental modeling of the occluded and unoccluded ureter

“…Notably, the majority of side-holes experienced WSS levels that are anticipated to favor significant accumulation of crystals and may, therefore, suffer from partial or complete occlusion. 19 Previous computational studies have also consistently shown that a significant proportion of side-holes is not involved in flow exchange between the stent and ureter; 12,18,38 however, the correlation between WSS levels and particle accumulation at side-holes within a full-scale model of the stented ureter has not been previously investigated.…”

“… 11 In a more recent CFD investigation, the same group evaluated the flow performance of stents with differing diameter, using ureter models presenting varying levels of stenosis. 12 Stents with smaller diameter had superior drainage performance, including within ureter models presenting mild-to-severe stenoses. Further investigations on the function of side-holes and urine flow distribution in the stented ureter have been carried out in a CFD study by Amitay-Rosen et al 13 Their numerical model replicated either a circumferential occlusion of the ureter or an external pressure applied on one side of the ureter wall.…”

Influence of Graft Ureter Length, a Donor-Related Factor, on Urinary Tract Infections After Living-Donor Kidney Transplantation: A Single-Center Analysis of 211 Cases

“…According to previous studies, the ureter tapers caudally from the pyeloureteral transition (5.67 ± 0.94 mm) to a small diameter (3.96 ± 0.65 mm) at the lower pole of the kidney. It then widens to its maximum diameter (5.11 ± 1.34 mm) at the abdominal ureter and retracts (3.59 ± 1.20 mm) at the pelvic margin across the common iliac artery( 19 , 20 ) ( Figure 2A ). The ureter was dissected at the lower level of the common iliac artery (median length of the removed ureter: 115.0 cm [95% CI, 100.0∼125.0 cm]) by the same surgeon, similar to the present study.…”

3D-Printing-Assisted Extraluminal Anti-Reflux Diodes for Preventing Vesicoureteral Reflux through Double-J Stents

“…Most urological procedures and treatments, such as lithotripsy, ureteroscopic procedures, prevention of ureteral stenosis, relief of hydronephrosis, and reduction in urological complications, require double-J (DJ) stents[ 1 - 7 ]. In general, these DJ stents are thin and hollow tubes with side holes composed of polyurethane material, and both ends are rolled up to hold the stent in the ureter[ 8 ]. The DJ stents are located in the ureter to enable urine drainage from the kidney into the bladder and to prevent contraction of the ureter after the removal of urinary stones[ 5 , 9 ].…”