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

Background/Objectives: 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. Methods: 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. Results: Transpapillary access was achieved in 95.7% of FG cases and 55.0% of F-UG cases (p = 0.003). Radiation exposure was significantly lower in the F-UG group (p < 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 (p = 0.092 and p = 0.210, respectively). Other outcomes, including the operative time, hospital stay, and stone-free rates, were similar between groups. Conclusions: 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.