Innovative use of the new pulsed-thulium: YAG laser for ureteroscopic lithotripsy: can the "kidney stone calculator" predict lithotripsy duration?

To assess the accuracy of Kidney Stone Calculator(KSC), a software designed for surgical planning, in predicting the duration of lithotripsy during flexible ureteroscopy(FURS) when using the novel pulsed-Thulium: YAG(p-Tm: YAG) laser. From February to August 2023, a single-center prospective study was conducted, including patients with kidney or ureteral stones through non-contrast computed tomography(NCCT), who underwent FURS with p-Tm: YAG laser lithotripsy. KSC used three-dimensional segmentation of the stones from NCCT images, along with an interactive user interface for laser settings, to estimate the stone volume(SV) and the lithotripsy duration(LD). The correlation between the estimated(esLD) and effective(efLD) lithotripsy duration was evaluated. A multiple linear regression analysis was conducted to identify preoperative and intraoperative factors affecting discrepancies between esLD and efLD. Twenty-eight patients were included with a median age of 55(48-74) years and 71% of men. Stone were located in the renal cavities(71%), ureter(21%) or both locations(8%). Median maximum stone diameter(MSD) and SV were respectively 14(11-30)mm and 1239(294, 2000)mm. Nine patients had a SV equal to or greater than 2000mm. EsLD and efLD did not differ(28 vs. 32 min, p = 0.8892), and were highly and positively correlated(r = + 0.90,p-value = < 0.001). Multivariate analysis indicated that the difference between estimated and effective lithotripsy were correlated with the stone volume(> 2000mm), the use of ureteral access sheath and for struvite stones. "Kidney Stone Calculator" can accurately estimate LD during FURS with the p-Tm: YAG laser. Variables such as stone volumes over 2000mm and stone composition could be integrated the estimation. KSC is the only software that estimates LD with Holmium: YAG, Thulium Fiber and p-Tm: YAG lasers.