Does Stone Entrapment With "Uro-Net" Improve Ho:YAG Laser Lithotripsy Efficiency in Percutaneous Nephrolithotomy and Cystolithopaxy?: an In Vitro Study

Abstract

Purpose: to test the effect of stone entrapment on laser lithotripsy efficiency. Materials and Methods: Spherical stone phantoms were created using the BegoStone® plaster. Lithotripsy of one stone (1.0g) per test jar was performed with Ho:YAG laser (365µm fiber; 1 minute/trial). Four laser settings were tested: I-0.8J,8Hz; II-0.2J,50Hz; III-0.5J,50Hz; IV-1.5J,40Hz. Uro-Net (US Endoscopy) deployment was used in 3/9 trials. Post-treatment, stone fragments were strained though a 1mm sieve; after a 7-day drying period fragments and unfragmented stone were weighed. Uro-Net nylon mesh and wire frame resistance were tested (laser fired for 30s). All nets used were evaluated for functionality and strength (compared to 10 new nets). Student's T test was used to compare the studied parameters; significance was set at p < 0.05. Results: Laser settings I and II caused less damage to the net overall; the mesh and wire frame had worst injuries with setting IV; setting III had an intermediate outcome; 42% of nets were rendered unusable and excluded from strength analysis. There was no difference in mean strength between used functional nets and non-used devices (8.05 vs. 7.45 lbs, respectively; p = 0.14). Setting IV was the most efficient for lithotripsy (1.9 ± 0.6 mg/s; p < 0.001) with or without net stabilization; setting III was superior to I and II only if a net was not used. Conclusions: Laser lithotripsy is not optimized by stone entrapment with a net retrieval device which may be damaged by high energy laser settings.