High-Frequency Dusting Versus Conventional Holmium Laser Lithotripsy for Intrarenal and Ureteral Calculi

摘要

Introduction: The efficiency of holmium laser lithotripsy for urolithiasis depends upon several factors, including laser pulse energy and frequency and stone composition and retropulsion. This study investigates the complex interplay between these factors and quantifies lithotripsy efficiency using different laser settings in a benchtop kidney and ureter model. Materials and Methods:In vitro caliceal and ex vivo porcine ureteral models were constructed. Calcium oxalate monohydrate stones were fragmented using a 200-m laser fiber. In the caliceal model, stone fragmentation and vaporization rates at settings of 0.6J/5Hz, 0.2J/15Hz, and 0.2J/50Hz were compared. In the ureteral model, fragmentation time, retropulsion rate, fragmentation rate, and fragmented stone weight were compared at settings of 0.6J/5Hz and 0.2J/15Hz. Retropulsive forces generated at 0.6J/5Hz, 0.2J/15Hz, and 0.2J/50Hz settings were compared. Analysis was performed using Student's t-test and one-way ANOVA. Results: In the caliceal model, the 0.6J/5Hz setting fragmented and vaporized stones at a higher rate than the 0.2J/15Hz setting (0.072 vs. 0.049mg/s; p<0.001). However, when the 0.2J energy setting was combined with the 50Hz frequency, the fragmentation rate (0.069mg/s) was similar to the fragmentation rate at 0.6J/5Hz (0.072mg/s; p=0.677). In the ureteral model, the 0.6J/5Hz setting produced higher fragmentation rates (0.089 vs. 0.049mg/s; p<0.001), but resulted in significantly lower fragmented stone weight overall (16.815 vs. 25.485mg; p=0.009) due to higher retropulsion rates (0.732 vs. 0.213mm/s; p<0.001). Retropulsive forces decreased significantly when pulse energy decreased from 0.6 to 0.2J (0.907 vs. 0.223N; p<0.001). Frequency did not affect retropulsive force at 15 and 50Hz settings (0.223 vs. 0.288N; p=0.509). Conclusions: Laser lithotripsy of calcium oxalate monohydrate stones in the ureter should be performed using the low-energy, moderate-frequency dusting setting to minimize retropulsion and maximize efficiency. In the renal calix, the low-energy high-frequency setting performed similarly to the high-energy low-frequency setting.