Learning curve in flexible ureteroscopy for renal stones: A propensity score-matched study.

OBJECTIVE: To assess the learning curve and evaluate the impact of surgical experience related to the outcomes of flexible ureteroscopy (fURS) for upper urinary tract stones. METHOD: We evaluated retrospectively lithiasis fURS performed in our institution between January 2004 and December 2020. Patients were divided into two groups by the number of procedures performed by surgeon. Group 1 (G1) included the first 50 procedures, and group 2 (G2) the next cases. These groups were matched on baseline characteristics by a propensity score. Stones free rate (SFR) and complication rate (CR) were compared. Learning curves were realized using logistic curve with 95% confidence interval. RESULTS: After criteria exclusion and propensity score matching, 1548 procedures were analyzed (1:1, G1 and G2, n=774 procedures). A total of 29 surgeons were evaluated. The overall SFR was 68.4% without statistical difference between the two groups (G1=67.9% vs. G2=68.8%, P=0.72). The surgeon's experience was not associated with SFR (OR=1.15, 95% CI: 0.90-1.47), except in subgroup stones>2cm (OR=2.89, 95% CI: 1.29-6.46). The overall CR was 12.5%, mainly Clavien-Dindo grade I-II complications (96.2%). Surgical experience was not associated with CR (OR=1.06, 95% CI: 0.77-1.45). The overall logistic curves for probability of stone clearance and complication tended to be a flat slope. CONCLUSION: Impact of surgical experience on fURS for UUTS was not associated with SFR and CR. However, for stones larger than 2cm, surgeon's experience tended to be associated with SFR, but without impact on overall complications.