Endourology & laparoscopy

Abstract

Editorial Comment Surprisingly little progress has occurred in lithotripter technology over the last 2 decades, and even less has translated into improved clinical success. However, recent efforts have been underway to not only improve technological aspects of lithotripters but to optimize treatment parameters to improve the efficiency and success of stone fragmentation. Zhou and colleagues compared the efficiency of in vitro fragmentation of stone phantoms with a Dornier HM3 lithotripter using 3 different strategies for administering output voltage: stepwise increase in voltage, stepwise decrease in voltage and constant voltage, with all strategies delivering approximately the same overall acoustic dose. Although initially, fragmentation efficiency correlated with shock wave dosage, ultimately comminution efficiency was greatest when output voltage was increased in a stepwise fashion compared with a strategy of decreasing or constant voltage. These finding are consistent with 2 synergistic processes of stone fragmentation, one based on stress waves that are thought to be pivotal in initial stone fragmentation, and one based on cavitation that is responsible for completion of fragmentation to small, passable pieces. These findings have yet to be validated in an animal model or in the clinical realm; however, they suggest that a strategy of a stepwise incremental increase in shock wave voltage output may provide for more effective stone fragmentation while potentially reducing tissue injury. This is encouraging news; perhaps by slowing the rate of delivery of shock waves as suggested by a recent randomized trial and incrementally increasing the output voltage during SWL, stone free rates may be improved without further risking tissue injury and without the need for new lithotripter technology.