Abstract
Ureteric stents are clinically deployed to retain ureteral patency in the presence of an obstruction of the ureter lumen. Despite the fact that multiple stent designs have been researched in recent years, encrustation and biofilm-associated infections remain significant complications of ureteral stenting, potentially leading to the functional failure of the stent. It has been suggested that “inactive” side-holes of stents may act as anchoring sites for encrusting crystals, as they are associated with low wall shear stress (WSS) levels. Obstruction of side-holes due to encrustation is particularly detrimental to the function of the stent, since holes provide a path for urine to by-pass the occlusion. Therefore, there is an unmet need to develop novel stents to reduce deposition of encrusting particles at side-holes. In this study, we employed a stent-on-chip microfluidic model of the stented and occluded ureter to investigate the effect of stent architecture on WSS distribution and encrustation over its surface. Variations in the stent geometry encompassed (i) the wall thickness and (ii) the shape of side-holes. Stent thickness was varied in the range 0.3-0.7 mm, while streamlined side-holes of triangular shape were evaluated (with a vertex angle in the range 45°-120°). Reducing the thickness of the stent increased WSS and thus reduced the encrustation rate at side-holes. A further improvement in performance was achieved by using side-holes with a triangular shape; notably, a 45° vertex angle showed superior performance compared to other angles investigated, resulting in a significant increase in WSS within “inactive” side-holes. In conclusion, combining the optimal stent thickness (0.3 mm) and hole vertex angle (45°) resulted in a ∼90% reduction in encrustation rate within side-holes, compared to a standard design. If translated to a full-scale ureteric stent, this optimised architecture has the potential for significantly increasing the stent lifetime while reducing clinical complications.
Highlights
Ureteric stents are clinically deployed to retain ureteral patency and adequately decompress the kidney, by maintaining ureteral flow in the presence of an intrinsic or extrinsic obstruction.1–3 The most commonly used stent consists of a hollow polymeric tube residing within the ureter lumen, with curly ends at its extremities to achieve stable anchoring within both kidneys and the bladder
A further improvement in performance was achieved by using side-holes with a triangular shape; notably, a 45° vertex angle showed superior performance compared to other angles investigated, resulting in a significant increase in wall shear stress (WSS) within “inactive” side-holes
In Hole 1, inter-compartmental flow exchange occurred because of the presence of the obstruction [see pathlines in Figs. 4(c) and 4(d)]. This enforced a significant increase in mean WSS, which was equal to 0.054 Pa, 0.030 Pa, and 0.012 Pa for wall thicknesses of 0.3 mm, 0.5 mm, and 0.7 mm, respectively
Summary
Ureteric stents are clinically deployed to retain ureteral patency and adequately decompress the kidney, by maintaining ureteral flow in the presence of an intrinsic or extrinsic obstruction. The most commonly used stent (known as “double-J”) consists of a hollow polymeric tube residing within the ureter lumen, with curly ends at its extremities to achieve stable anchoring within both kidneys and the bladder. Ureteric stents are clinically deployed to retain ureteral patency and adequately decompress the kidney, by maintaining ureteral flow in the presence of an intrinsic or extrinsic obstruction.. The most commonly used stent (known as “double-J”) consists of a hollow polymeric tube residing within the ureter lumen, with curly ends at its extremities to achieve stable anchoring within both kidneys and the bladder. Since the introduction of the first stent by Finney in 1978,5 a large body of work has been carried out to redesign stents to scitation.org/journal/bmf improve their overall performance.. Since the introduction of the first stent by Finney in 1978,5 a large body of work has been carried out to redesign stents to scitation.org/journal/bmf improve their overall performance.6 Despite these efforts, encrustation and biofilm-associated infections remain significant complications of ureteral stenting, potentially leading to the functional failure of the stent. They are responsible for increased patient morbidity and healthcare costs, as they often require hospital re-admission and re-intervention.
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