Stone clearance times with mini-percutaneous nephrolithotomy: Comparison of a 1.5 mm ballistic/ultrasonic mini-probe vs. laser
Introduction: A limitation of mini-percutaneous nephrolithotomy (mPCNL) is the narrow working channel of mini-nephroscopes, typically restricting instrumentation to 5 French (F) or smaller. We evaluated the efficacy of the 1.5 mm Swiss LithoClast ® Trilogy (Trilogy) rigid probe and compared the results to consecutive cases performed with a 30 W Holmium:YAG (Ho:YAG) laser.
Methods: A retrospective review of 30 consecutive mPCNL cases using the Trilogy and 30 W Holmium laser was performed. A 12 F MIPS nephroscope with a 16.5 F access sheath and 6.7 F working channel was used for all mPCNL cases. The Trilogy was used with a disposable 1.5 mm x 440 mm probe with dual ultrasonic and ballistic energy. The Ho:YAG laser was used with a 550 micron fibre and a maximum of 30 W. Stone clearance time (SCT) was defined by the total time interval between activation of the lithotripter until insertion of the nephrostomy tube and measured in mm2/minutes. SCT included time for fragment retrieval, equipment adjustments, and rigid and flexible nephroscopy during and after lithotripsy.
Results: Eleven cases using a 1.5 mm Trilogy probe and 16 cases using a Ho:YAG laser met final inclusion criteria. Three cases using the Trilogy were excluded from final analysis due to conversion to alternative energy sources — two of those were upsized to standard PCNL and one was converted to laser. Mean stone diameter and density in the final Trilogy cohort was 26.7 mm and 1193 Hounsfield units (HU). Mean diameter and density in the laser cohort was 25.2 mm and 1049 HU. The mean stone area clearance time for Trilogy was 4.7±1.8 mm2/minute vs. 3.4±0.7 mm2/minute with Ho:YAG laser (p=0.21). For hard stones, defined as density >1000 HU, the Trilogy averaged 3.7±1.6 mm2/minutes, while the laser averaged 3.1±1.3 mm2/minutes (p=0.786). For soft stones, defined as <1000 HU, the Trilogy averaged 8.9±1.0 mm2/ minutes compared to the Ho:YAG, which averaged 3.6±1.8 mm2/minutes (p=0.019). No device-related complications occurred in either cohort.
Conclusions: The 1.5 mm mPCNL Trilogy probe was comparable to 30 W Ho:YAG laser for clearing hard stones. The Trilogy performed better than laser on soft stones with a HU density <1000 HU.
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