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

PURPOSE: Urinary stones can be successfully treated using a Holmium: Yttrium-Aluminum-Garnet (Ho: YAG) laser. Regarding success 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 mm(3) stone destruction per overall operating 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] mm(3); p=0.023) and (348±298 [SPS] vs. 525±429 [NPS2] mm(3); 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 mm(3)/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 individualized intraoperative decision making.