Femtosecond laser lithotripsy: a novel alternative for kidney stone treatment? Evaluating the safety and effectiveness in an ex vivo study

The Holmium (Ho:YAG) laser is presently the most extensively employed in laser lithotripsy for the management of kidney stones. Despite its adoption as the gold standard for laser lithotripsy, Ho:YAG laser lithotripsy poses three significant challenges, namely thermal effect, insufficient stone fragmentation, and stone displacement, which have garnered increased attention from urologic surgeons. Nowadays, the femtosecond laser is regarded as a potential alternative to the Ho:YAG laser due to its capacity to ablate diverse materials with minimal thermal effect. In our ex vivo investigation, we assessed the dimensions of ablation pits, the efficacy of ablation, the degree of stone fragmentation, the alterations in water temperature surrounding stones, and the degree of tissue damage associated with Femtosecond laser lithotripsy utilizing adjustable power settings (1–50 W). Our findings indicate that the ablation pits generated by the Femtosecond laser exhibited uniform geometries, and the effectiveness of ablation and fragmentation for Femtosecond laser lithotripsy were significantly and positively correlated with laser power. When the laser power remained constant, the Femtosecond laser with higher pulse energy demonstrated superior efficiency in stone ablation, but inferior performance in stone fragmentation. Conversely, the Femtosecond laser with higher pulse frequency exhibited the opposite behavior. Furthermore, the thermal effect increased proportionally with laser power, leading to a tentative recommendation of 10W laser power for future investigations. Our in vitro findings suggest that the Femtosecond laser holds promise as a safe and effective alternative to holmium lasers.