Challenging the gold standard: Flank-free modified supine versus prone position in the management of complex renal stones.

Abstract

Purpose: The purpose of this study was to compare the safety, efficacy, and operative outcomes of the flank-free modified supine position versus the standard prone position for percutaneous nephrolithotomy (PCNL) in patients with complex renal stones.

Materials and methods: In this prospective randomized controlled trial (May 2022-November 2024), 178 patients with complex renal stones (Guy's Stone Score II-IV) were randomized 1:1 to undergo PCNL in the flankfree modified supine position (n = 89) or standard prone position (n = 89). The primary outcome was stone-free rate (SFR), defined as no residual fragments ≥ 4 mm on noncontrast computed tomography at 3 months. Secondary outcomes included operative time, hemoglobin drop, and complications graded using the Clavien-Dindo classification.

Results: Baseline characteristics and stone complexity were comparable between groups. Mean operative time was significantly shorter in the supine group (72.61 ± 8.07 vs. 92.80 ± 6.90 min; P < 0.001). SFR was 91.0% in the supine group versus 85.4% in the prone group (P = 0.245). There were no significant differences in hemoglobin drop or overall complication rates. The prone group utilized a higher proportion of lower pole punctures (74.6% vs. 61.8%), whereas the supine group required significantly more middle (22.5% vs. 9.0%) and upper pole (11.2% vs. 2.2%) access (P < 0.05).

Conclusion: Flank-free modified supine PCNL is a safe and effective alternative to standard prone PCNL for complex renal stones, providing significantly shorter operative time and favorable ergonomics without compromising stone clearance or safety.