Presented by: Jason Y. Lee MD, MHPE
Division of Urology, Department of Surgery, University of Toronto, University Health Network

Introduction

After demonstrating efficacious in vitro efficacy, the thulium fibre laser (TFL) has been released to market with promising initial clinical results. At our institution, reduced TFL lithotripsy was observed during certain stone cases. The purpose of this study was to identify whether stone composition affects TFL lithotripsy.

Materials

We conducted a retrospective review of all patients that had undergone TFL laser lithotripsy (SOLTIVE^TM SuperPulsed Laser System, Olympus America) at our institution between July 2020 and January 2022. Only patients with stone analysis data were included. Demographic and stone-specific data were collected and correlated with subjective (surgeon rating) and objective measures of lithotripsy efficacy.

Results

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A total of 91 patients were included in the study. Mean age was 59.8 years, mean BMI was 27.5, and mean stone volume was 438 mm³ (Table 1). Stone composition correlated with patient age (p=0.008), mean stone density (p<0.001), mean stone volume treated per laser time (p=0.033), and surgeon rating of TFL efficacy (p<0.001). Lower surgeon rating of TFL efficacy correlated with higher stone density (p=0.011), greater number of laser pulses used (p=0.035), and stone composition (p=0.035). Stones composed of CaPO₄ + struvite had lower surgeon rating of TFL efficacy, while pure uric acid and mixed CaOx + uric acid stones had the best rating. Stone location correlated with total energy (J) used (p=0.036) but not with any other TFL efficacy measures or stone composition (α=0.05).

Conclusion

Stone composition, particularly CaPO₄ + struvite, seems to be associated with reduced TFL lithotripsy. A limitation of our retrospective study is that we were unable to differentiate between brushite and apatite stones. The relationship between stone composition and TFL lithotripsy requires further evaluation prospectively, while basic science research is required to understand the biophysical mechanisms of reduced lithotripsy.

Funding

None.

Lead Authors

Simon Czajkowski, MSc, MBE (Bioethics)
Division of Urology, Department of Surgery, University Health Network

Co-Authors

Bruce Gao, MD
Division of Urology, Department of Surgery, University of Toronto