Holmium versus thulium fibre laser for ureteroscopy and lithotripsy: When, why and how?

Background: The holmium: yttrium-aluminum-garnet (Ho:YAG) laser, which has been the gold standard for lithotripsy, has evolved to high frequency systems with pulse modulation. However, there is now an alternative laser for lithotripsy - the thulium fiber laser (TFL).Purpose: While bench testing has shown superior fragmentation performance of the TFL compared to Ho:YAG, initial clinical results for ureteroscopy have not been as dramatic. We therefore analyze laboratory and clinical studies comparing these two laser platforms. Our goal is to offer insights into when and why to choose one laser over the other for ureteroscopy, along with strategies for optimal use.Methods: In this narrative review we describe the characteristics of each laser and provide an overview of the in vitro studies comparing Ho:YAG and TFL for fragmentation, retropulsion and heat generation. We also review evidence from prospective comparative effectiveness clinical trials for ureteroscopy and lithotripsy. We provide our schema for when we use each laser for ureteroscopy, the rationale and our approach with laser settings.Conclusions: Ho:YAG and TFL have distinct wavelengths, pulse duration, peak power, and water absorption parameters that make them suitable for different scenarios. The decision between which laser to choose rests upon individual preferences and confidence levels of use, with the ultimate priority for safe patient use.