Will Stone Density Stop Being a Key Factor in Endourology? the Impact of Stone Density on Laser Time Using Lumenis Laser p120w and Standard 20 W Laser: A Comparative Study

Introduction and Objectives: Ureteroscopy is the gold standard for most urinary tract calculi. Our institute recently incorporated a powerful 120 W holmium laser machine integrating innovative technology (Lumenis^® MOSES Pulse^TM120H Holmium:YAG laser; Lumenis Ltd.). In this retrospective comparative study, we evaluated the influence of stone density on laser dusting time in a high-power 120 W laser machine vs a standard 20 W machine (Dornier Medilas^® H20 Holmium:YAG laser; Dornier Ltd.) Methods: We conducted a retrospective review of medical records of patients who underwent ureteroscopy during the years 2013-2018 for a solitary stone. Stone and clinical characteristics, among other parameters, have been evaluated, including the total laser time until complete stone dusting. Results: Among 631 eligible patients, 462 were treated with a 20 W standard laser and 169 patients with a p120w laser machine. Overall laser time was less than half with p120w laser vs d20w (195 seconds vs 397.14 seconds, p-value <0.001). Multivariate regression demonstrated 234.91 seconds shorter laser time with a p120w laser while controlling confounders such as stone volume, hydronephrosis, and location (p value <0.0001). This pattern was demonstrated in all stone densities. The association between laser dusting time per stone volume and stone density demonstrated relatively constant laser time when using p120w laser, even for hard stones. When the standard 20 W laser was used, laser time was longer in each stone density. Moreover, a stone density of 1164 HU and more demonstrated an upward shift of laser time to stone density curve in standard d20w laser group only. Conclusions: Time to complete stone dusting using p120w laser is extremely shorter, approximately half, comparing with the standard 20 W laser. This pattern is robust and even exponential when evaluating laser time per stone density, especially in hard stones. A new horizon of powerful innovative laser technology will enable to improve endourology practice and patients' care.