Laser to stone interaction: how do lasers break stones ? a systematic review

Advances in laser lithotripsy have driven major progress in endourology over the past three decades. Although Holmium:YAG and, more recently, thulium-based lasers are widely used, the fundamental mechanisms governing laser-to-stone interaction remain incompletely understood and controversial. A systematic literature search was performed in MEDLINE/PubMed and Embase from database inception to December 2025. Experimental and translational studies investigating physical, thermal, chemical, or mechanical mechanisms of laser-to-stone interaction were included. Data on experimental models, laser parameters, environmental conditions, measurement techniques, and mechanistic outcomes were extracted. Methodological quality was assessed using the QUINN scale. Because of the marked heterogeneity in study designs, populations, and outcome measures, a meta-analysis could not be performed. Consequently, the findings were synthesized through a structured narrative systematic review. Twenty experimental studies published until 2025 were included. Early investigations primarily supported photothermal and thermochemical ablation under contact conditions. Contemporary studies employing high-speed imaging, hydrophone measurements, and controlled environmental manipulation consistently demonstrated that non-contact dusting is dominated by cavitation-driven erosion mediated by asymmetric bubble collapse. Recent evidence further identified confined intra-crater bubble expansion as the important mechanism underlying fracture of impacted stones. Mixed thermal and mechanical effects were observed under transitional conditions, particularly in the presence of pulse modulation and optimized energy transmission. Methodological quality improved over time, with the highest rigor observed in recent mechanistic studies. Laser lithotripsy is governed by distinct, strategy-dependent physical mechanisms rather than by a single dominant process. Contact ablation is primarily photothermal, non-contact dusting is cavitation-driven, and impacted stone fracture relies on confined bubble expansion. These findings support an integrated mechanistic framework linking laser settings, fiber positioning, environmental conditions, and stone geometry. This framework provides a rational basis for optimizing clinical strategies and guiding future technological development in laser lithotripsy.