EX-VIVO COMPARISON OF 4 LITHOTRIPTERS COMMONLY USED IN THE URETER - WHAT DOES IT TAKE TO PERFORATE

We hoped to determine the number of pulses and energy needed to create acute ureteral perforations with four different lithotripters in a re producible ex vivo model. A simple model was constructed to control va riables in the testing such as wall thickness, intraluminal pressure, distance between the probe tip and ureter, and power delivered to tiss ue. Segments of domestic pig ureter were prepared and fixed in positio n in a normal saline (NS) bath at room temperature. We then attempted perforation with the holmium:YAG (HoL) laser, coumarin pulsed-dye lase r (CdL), electrohydraulic lithotripter (EHL), and pneumatic impactor ( PI) by placing the instrument probes at right angles to the ureteral w all. The ureter was filled with a methylene blue-stained solution of N S at 90 cm H2O pressure via a urodynamics catheter, and perforation wa s recorded on initial extravasation of dye. The endpoints measured wer e time to perforation and total energy required. At 0.5 mm of separati on between the wall and probe, the Hot perforated the ureter in an ave rage of 2 seconds and 0.01 kJ delivered at 5 W (10 Hz and 0.5 J/pulse) . The EHL perforated at an average of 24.44 +/- 8.77 seconds and a tot al energy of 0.01 +/- 0 kJ. The CdL was able to perforate but at much longer intervals (257.51 +/- 99.08 seconds) and higher energy levels ( 12.88 +/- 4.95 kJ) on average than either the EHL or Hot. Lastly, the PI was unable to perforate the ureter in more than 6 continuous minute s of application. In addition, me found that at 2-mm separation betwee n the Hot probe tip and the ureteral wall, acute perforation was not p ossible even at very high power settings. We conclude that although ea ch endoscopic lithotripter has advantages as well as disadvantages, in this ex vivo model, it was clear that the Hot and EHL can easily perf orate the ureter and must be used with vigilance. It was found that at 2 mm of separation between the probe and target, the Hot, was unable to perforate acutely. The CdL and PI were associated with a much highe r safety index, and the PI was unable to produce ureteral perforation.