Tandem ureteral stents drainage lowers renal pelvis pressure in malignant ureteral obstruction: Experimental and computational models

Abstract

Malignant ureteral obstruction may lead to impaired renal function and requires drainage by a percutaneous nephrostomy tube or an internal ureteric stent. Usage of stiff tandem ureteral stents may decrease stent failure rates. In this paper we combined computational and in vitro models to examine the flow in a malignant ureteral obstruction (MUO) managed by 4 methods of drainage: single soft stent, single stiff stent, soft tandem ureteral stents, and stiff tandem ureteral stents. Pressure at the renal pelvis was the primary outcome of the computational and in vitro models. Different drainage modalities were compared using ANCOVA. Results of computational and in vitro models agreed completely. Drainage by stiff tandem ureteral stents provides lower renal pelvis pressure levels compared with single and soft stents (p < 0.001), especially for high levels of external pressure. Usage of stiff tandem ureteral stents may decrease stent-failure rates and postpone the need for percutaneous nephrostomy tube insertion.

Introduction

In healthy individuals, pressure in the urinary collecting system during urine transport is low. However, obstruction of urinary flow may lead to increased pressure, resulting in impaired ability to concentrate urine and severe flank pain. When the etiology of the obstruction cannot be treated directly as in the case of non-resectable external tumors, drainage of the upper urinary tract is mandatory (Brin et al., 1975) either by a percutaneous nephrostomy tube (PCN) or an internal ureteric stent. Both methods successfully decrease pressure, relieve pain, and normalize kidney function. As the tumor enlarges, the flow field through and alongside the stent is interrupted and failure of the drainage occurs in up to 38% of the cases (Ganatra and Loughlin, 2005, Izumi et al., 2011). Several treatment options have been developed in order to withstand the compressive forces of the tumor: usage of a stiff stent, two stents (tandem ureteral stents, TUS), metallic stent or a PCN. While metallic stents have been extensively studied in the literature (Blaschko et al., 2007, Liatsikos et al., 2010, Liatsikos et al., 2008), the effects of ureteral drainage with different combinations of soft/stiff single stent/TUS on external ureteral obstruction have been poorly investigated. Recently, Haifler and colleagues described a large cohort of patients undergoing TUS insertion and demonstrated the safety and efficacy of the procedure (Haifler et al., 2020). In this paper we examined the flow in computational and in vitro models of malignant ureteral obstruction (MUO) managed by 4 methods of drainage: single soft stent, single stiff stent, soft TUS, stiff TUS.