Comparing outcomes of thulium fiber laser versus high-power Holmium:YAG laser lithotripsy in pediatric patients managed with RIRS for kidney stones. A multicenter retrospective study.

Background: The aim of this study was to evaluate thulium fiber laser (TFL) safety and efficacy compared to high-power (HP) Holmium:YAG laser in pediatric patients who have undergone retrograde intrarenal surgery (RIRS) for kidney stones.

Methods: We retrospectively reviewed data from pediatric patients who underwent RIRS for kidney stones between 2018 and 2020. Complications were assessed 4-6 weeks postoperatively. Stone-free (SF) was defined as the absence of visible fragments or as the presence of a single residual fragment ≤2 mm at 3 months postoperative imaging. Student's t-test for continuous variables, and χ and Fisher's Exact Test for categorical variables were used to compare outcomes between patients treated with HP Holmium:YAG (group 1) and TFL (group 2). Univariate (UVA) and multivariate (MVA) logistic regression analyses were performed to predict SF-associated factors.

Results: Data from 126 pediatric patients were analyzed, 97 in group 1 and 29 in group 2. Preoperative characteristics were similar between cohorts. No major complication occurred in both groups. Group 2 had a shorter operative time (mean time 49.5 vs. 64.3 min, P=0.024). SF rate was 81.4% and 89.7% (P=0.45) and reintervention rate was 14.4% and 6.89% (P=0.046) in group 1 and 2, respectively. At UVA and MVA, the type of laser did not influence SF rate. However, prestenting and single stones were positively associated with SR rate.

Conclusions: Both laser technologies are safe and effective and showed similar SF rates. TFL showed less operative time and lower re-intervention rate compared to HP Holmium:YAG. Further prospective studies are needed to corroborate our findings.