Rethinking ureteral stent design: Do more side holes improve performance?

Ureteral stents, particularly double-J stents, are widely used to maintain urinary flow in the presence of ureteral obstruction. These stents are designed with side holes along their length to promote urine drainage and prevent complications. Despite their effectiveness in restoring urinary flow, ureteral stents are prone to complications such as encrustation (mineral buildup) and biofilm formation, which can lead to infections and blockages. Vesicoureteral reflux (VUR), described as urine flowing backwards from the bladder to the kidney, is another common complication, raising the risk of infections, especially pyelonephritis, and increased kidney pressure. Several stent design upgrades were proposed to address these issues, but limitations remain. This study explores the functionality of additional side holes (ASHs) at both ends of the stent, with particular emphasis on their performance during VUR. Using computational modelling, we evaluate how these ASHs influence fluid dynamics, wall shear stress (WSS), and flow pathways during normal urine production and VUR. Results show that the ASHs redistribute the fluid exchange between the stent lumen and the ureter during VUR, altering the WSS patterns. Additionally, slight ASH diameter differences (i.e., 0.7 mm, 1 mm, and 1.2 mm) lead to significantly different WSS distributions. Larger diameters promote more fluid exchange but reduce local mean WSS, a factor crucial for preventing biofilm attachment. Our findings suggest that tailored design optimization of ASHs could provide simple solutions to alleviate the various complications for patients with indwelling stents.