1576

IN VITRO ASSESSMENT OF THE CYBERWAND INTRACORPOREAL LITHOTRIPTOR

Samuel C Kim*, Brian R Matlaga, Molly E Jackson, Indianapolis, IN; Ramsay L Kuo, Philadelphia, PA; James C Williams, Jr, James A McAteer, James E Lingeman, Indianapolis, IN

INTRODUCTION AND OBJECTIVE: The Cyberwand (Cybersonics, Erie, PA) is a novel intracorporeal lithotriptor that incorporates two concentric probes driven at different frequencies by a single ultrasonic hand piece. We performed a study to compare this device to the Lithoclast Ultra (Boston Scientific, Natick, MA), which we have previously demonstrated in vitro to be the most efficient commercially available intracorporeal lithotripsy device (J Urol 170:1101-1104, 2003).

METHODS: An in vitro test system was used to assess the efficiency of stone penetration for the Cyberwand and the Lithoclast Ultra. The devices were mounted upright (probe tip up) in a modified irrigation sheath. A gypsum artificial stone was centered on the probe tip, and a mass was placed atop the stone to provide constant force. Output of the Cyberwand was pre-set by the manufacturer. For the Lithoclast Ultra, we used a pneumatic frequency of 12 Hz with an ultrasonic power setting of 100%, optimal settings as determined from previous in vitro tests (J Endourol, 18:153-156, 2004). The time required for complete stone penetration was assessed. Differences in mean stone penetration times were compared using ANOVA.

RESULTS: The mean penetration time for the Cyberwand was significantly less than for the Lithoclast Ultra (4.77 seconds, SD 0.63 vs. 8.09 seconds, SD 0.55, p<0.0001). Neither device exhibited any difficulties with overheating, occlusion, or other malfunction.

CONCLUSIONS:Initial assessment using our “hands-free” in vitro test system - in which stone penetration time is not affected by operator bias - suggests that the Cyberwand is a very efficient lithotrite. The Cyberwand is a simpler, more ergonomic device than the Lithoclast which combines both an ultrasonic and a pneumatic device.

1577

FLOW CHARACTERISTICS OF TWO IPSILATERAL AND NOVEL URETERAL STENTS: HOW WELL DO THEY PROVIDE RELIEF OF URETERAL OBSTRUCTION?

Beng Jit Tan*, New Hyde Park, NY; Jason M Hafron, David M Hoenig, Bronx, NY; Benjamin R Lee, Arthur D Smith, New Hyde Park, NY

INTRODUCTION AND OBJECTIVE: There is a high failure rate of single indwelling ureteral stents in the management of patients with extrinsic ureteral obstruction. The use of two parallel ureteral double-J stents has shown promising results in patients when a single stent has failed. However, no studies on the flow characteristics of double stented ureters have been reported to date. Using a novel ex vivo porcine model to measure ureteral flow within an extrinsically obstructed renal unit, dual internal parallel ureteral stents and two prototype double lumen ureteral stents were evaluated to assess their efficacy in relieving ureteral obstruction.

METHODS:Sixteen renal units with intact ureters were harvested from eight adult Yorkshire female pigs. To quantify flow, the kidneys were infused at a constant pressure and the corresponding ureteral drainage was measured over a defined time interval. Flow was measured in an unstented ureter (control), and stented ureters with a standard 7 Fr double pigtail stent, two ipsilateral 7 Fr double pigtail stents, 7 Fr novel double lumen stent designed with both proximal lumens open (SP-1)and a 7 Fr novel double lumen stent with one proximal lumen closed (SP-2). Each stent was assessed for intra- and extra-luminal flow in an obstructed and non-obstructed system.

RESULTS: Dual ipsilateral standard stents and prototype double stents achieve better flow down the ureter than with one standard stent. When both stent lumens were obstructed, there was still good drainage around the stents. There was still good drainage through the stent lumens and within the potential space between the stents even after the ureter was ligated, simulating extrinsic obstruction. The novel double stents work just as well as dual ipsilateral stents provided that the proximal ends were not closed.

CONCLUSIONS:Two parallel ipsilateral ureteral stents and double lumen prototype stents preserve both intraluminal and extraluminal flow between the stents in extrinsically obstructed ureters.

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