Transition learning curve of a single surgeon performing ultrasound-guided modified lateral position percutaneous nephrolithotomy

BACKGROUND: Ultrasound-guided percutaneous nephrolithotomy (PCNL) performed in the modified lateral position offers advantages in ergonomics, airway control, and radiation reduction. However, evidence describing the transition learning curve of surgeons previously trained in fluoroscopy-guided prone PCNL remains limited. This study evaluates learning progression, surgical efficiency, and safety outcomes as an experienced fluoroscopic surgeon adopts an ultrasound-guided modified lateral PCNL technique. MATERIALS AND METHODS: This retrospective study included 70 consecutive patients who underwent ultrasound-guided modified lateral PCNL with extended legs, performed by a single surgeon experienced in fluoroscopy-guided prone PCNL. Patients were divided chronologically into three groups (cases 1-25, 26-50, and 51-70). Operative parameters, puncture characteristics, fluoroscopy time, stone-free rate (SFR), and complications were analyzed. Learning progression was assessed using cumulative summation (CUSUM) analysis based on operative time. RESULTS: Progressive improvements in performance were observed across the series. The proportion of single-attempt punctures increased from 40% to 75% (p=0.023), while upper calyceal access increased from 8% to 70% (p