Endoscopic Verification of Transpapillary Access in Supine Percutaneous Nephrolithotomy: A Prospective Pilot Study Comparing Freehand Ultrasound and Fluoroscopy Guidance.

: Achieving renal access is a key step in percutaneous nephrolithotomy (PNL), with transpapillary access considered the safest anatomical approach. This prospective pilot study aimed to compare the effectiveness of freehand ultrasound-guided (F-UG) versus fluoroscopy-guided (FG) punctures in achieving anatomically accurate transpapillary access during supine PNL, confirmed by endoscopic visualization. Perioperative and postoperative outcomes were also evaluated. : Forty-three patients undergoing supine PNL for renal pelvic or lower calyceal stones were prospectively enrolled and assigned to either the FG group (n = 23) or F-UG group (n = 20). Following renal access, intraoperative flexible ureteroscopy confirmed the anatomical nature of the puncture (transpapillary vs. nonpapillary). The puncture time, fluoroscopy time, operative time, complications (Clavien-Dindo classification), transfusion requirement, hospital stay, and one-month stone-free rates were recorded. : Transpapillary access was achieved in 95.7% of FG cases and 55.0% of F-UG cases ( = 0.003). Radiation exposure was significantly lower in the F-UG group ( < 0.001). Complication (15.0% vs. 0.0%) and transfusion rates (10.0% vs. 0.0%) were higher in the F-UG group but not statistically significant ( = 0.092 and = 0.210, respectively). Other outcomes, including the operative time, hospital stay, and stone-free rates, were similar between groups. : FG puncture is more effective for achieving transpapillary access, while F-UG significantly reduces radiation exposure. The endoscopic confirmation method may provide a reference for future comparative studies on access techniques in PNL.