Influence of the laser pulse shape in the treatment of stones in the upper urinary tract

Abstract

Purpose: Urinary stones can be successfully treated using a Holmium: Yttrium-Aluminum-Garnet (Ho: YAG) laser. Regarding suc-cess rates, laser pulse energy, frequency, and pulse width are well-known contributing factors. Whether the pulse shape might be a further factor influencing the laser efficiency is unclear. This study aimed to evaluate different modes of laser pulse shapes in a real-world setting. Materials and Methods: The Dornier Medilas® H Solvo (Weßling, Germany) was used in the treatment of ureter and kidney stones. Patients were randomized into standard pulse shape (SPS) and new pulse shape groups (NPS1; ureter) and (NPS2; kidney pelvis), depending on the stone localization. The primary endpoint was laser efficiency defined as mm3 stone destruction per overall oper-ating time. Secondary endpoints encompassed number of stone recoveries and stone-free rate. Results: Altogether 145 patients (24 SPS vs. 32 NPS1; 51 SPS vs. 38 NPS2) were included. No differences in sex, age, body mass index, stone localization and stone composition were found, except for preoperative stone size (133±95 [SPS] vs. 197±139 [NPS1] mm3; p=0.023) and (348±298 [SPS] vs. 525±429 [NPS2] mm3; p=0.042). Regarding the primary endpoint, a significant increase in laser efficiency could be detected for the NPS1 and NPS2 groups compared to the SPS groups (39.9±44.9 vs. 28.8±30.2 and 51.7±61.3 vs. 22.4±24.2 mm3/min [mean±standard deviation]). No statistically significant differences were found for secondary endpoints and perioperative complication rates. Conclusions: Efficiency of the Ho: YAG laser can be positively influenced by different pulse shapes. This adds the variable of indi-vidualized intraoperative decision making.