Percutaneous renal stone extraction: in vitro study of retrieval devices

Traditionally, percutaneous stone extraction has relied on the use of 2-prong and 3-prong graspers, which are prone to causing trauma to the urothelium. We evaluate the efficiency of stone removal with a novel tipless stone basket designed specifically for percutaneous procedures.

A 3, 5 and 8 mm human calculus were placed in the calix of a percutaneous renal model. A 26Fr Storz nephroscope (27093B, Storz Medical AG, Kreuzlingen, Switzerland) was inserted through a 30Fr Amplatz sheath into the model with camera input from a Storz telecam SL-NTSC feeding to a 20-inch Sony Triniton monitor (Sony Corp of America, New York, New York). Operators were randomized to start stone extraction with a Storz 3-prong grasper (27090RB) or a Cook 12Fr Perc-NCircle (38 cm) (Cook Urological, Inc., Indianapolis, Indiana). Subsequent testing alternated between the 2 devices until 10 extraction attempts were conducted with each device. Time to extraction of all 3 calculi and number of inadvertent withdrawals of the sheath were recorded. Three experienced operators tested each device.

Stone extraction times were shorter with the Cook Perc-NCircle than the 3-prong grasper for all operators. Mean time for stone extraction was 25.3 +/- 11.2 seconds for the Perc-NCircle compared to 35.1 +/- 18.5 seconds for the 3-prong grasper (p = 0.016). Loss of access by inadvertent removal of the Amplatz sheath occurred in 53% of the attempts with the 3-prong grasper compared to 7% of attempts with the Perc-NCircle.

The Cook Perc-NCircle facilitates a more expeditious approach to percutaneous stone removal with less risk of sheath withdrawal.