Abstract
BackgroundTo compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment.MethodsWe employ an in vitro ureter-stent experimental set-up, with latex tubing simulating flexible ureters attached to vessels simulating renal units and bladders. The flow behavior of five ureteral stents—polymeric 8F, tandem 6F, tandem 7F, endopyelotomy and metal—was tested under a ureteral deformation configuration of 40°, with 2000 g external force over a 3.5 cm length of the ureter. A constant fluid flow was applied through the ureter-stent configurations, and pressure fluctuations in the renal unit were monitored. We considered a renal unit pressure of 10 cmH2O or flow discontinuation in the bladder as stent failure. Urine containing debris was mimicked by use of a colloidal solution.ResultsOf all assessed ureteral stents, under EUO conditions, only the single 8F stents remained patent throughout the length of the experiment. All other stents—tandem 6F and 7F, single 7F, metal and endopyelotomy—displayed limitations.ConclusionsTandem and metal stents show no superiority over large luminal polymeric stents for EUO treatment in this in vitro model. Larger luminal stents offer excellent resistance to external pressure and allow adequate colloidal flow. The need for frequent exchange and bladder irritation should also be considered in the choice of stent configuration for treatment of kidney drainage under EUO.
Highlights
To compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment
We showed previously [18, 21] that deformation/compression alone, using a solution without colloids, are not generally sufficient to lead to stent failure under EUO, in tests with 4.8F, 6F, 7F and 8F stents
We found, too, in preliminary measurements, that like the single 8F stent, the tandem 6F and 7F stents, the Resonance® metallic stent, and the 7F/14F endopyelotomy stent are unaffected by realistic deformation/compression
Summary
To compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment. As many as ~ 50% of ureteral stents placed to treat EUO fail (in terms of drainage, leading to renal failure and hydronephrosis), often within weeks [1]. While the exact mechanism(s) for stent failure is unclear, large caliber [2, 3], tandem [4,5,6,7,8,9] and metal [10,11,12,13,14,15,16,17] stent designs have been suggested to overcome this problem. We employed an in vitro experimental setup [18] to investigate the influence of both ureteral deformation and compression, and the synergistic effect of colloid presence in the fluid, on stent patency
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