Introduction: To compare the outcomes of using low power (up to 30W) vs high power (up to 120W) holmium lasers in paediatric retrograde intrarenal surgery (RIRS) and to analyse if the choice of scopes; lasering techniques and the use of access sheath have any influence on the final outcomes. Methods: We performed a retrospective, multicentre study in a paediatric population (= 18 years of age), who underwent RIRS with holmium laser for treatment of kidney stones between January 2015 and December 2020. Patients were divided into two groups according to laser used: high power holmium laser and low power holmium laser. Clinical, perioperative variables and complications were analyzed. Outcomes were compared between groups using Student's T-test for continuous variables, and for categorical variables were used Chi-square and Fisher's exact test. A multivariable logistic regression analysis model was also performed. Results: 314 patients from 9 centres were included. A high-power holmium laser was used in 97 patients, whereas 217 patients underwent low power holmium laser with a mean age of 10.01 and 9.54, respectively. Clinical and demographic variables were comparable between both groups, except for stone size where the low power group treated slightly larger stones (mean 11.11 mm vs 9.70 mm; p 0.018). In the high-power laser group, a reduction in surgical time was found (mean 64.29 min vs 75.27 min; p 0.018) with significantly higher SFR (mean 81.4% vs 59%; p <0.001) and faster operative time (mean 75.27 min vs 64.29min; p 0.018). We found no statistical differences in complications rates but overall number of complications was higher in low-power holmium laser group. The multivariate logistic regression model also shows statistically significant results that the low-power holmium laser group has a lower SFR, especially in larger lithiasis (p=0.011or multiple stones, p<0.001). Conclusions: Our real world pediatric multicenter study favors high-power holmium laser and establishes is safety and efficacy in children. With innovations, it would be best adapted to provide the best possible SFR results in a single session for children without compromising safety. SOURCE OF Funding: NIL
