Supine Versus Prone: A Comparison of Percutaneous Nephrolithotomy Outcomes in Obese Patients

Abstract

Introduction: Obesity increases both the incidence of nephrolithiasis and the technical challenges of percutaneous nephrolithotomy (PCNL). Evidence comparing supine and prone PCNL in obese patients remains scarce, with only one prior study worldwide. We compared perioperative outcomes of the two positions in the largest Asian obesespecific cohort to date. Methods: We retrospectively reviewed all adults with body mass index > 30 kg/m 2 who underwent unilateral PCNL at Sarawak General Hospital and Sarawak Heart Centre between May 2020 and April 2023. Patients who had bilateral PCNL or concomitant procedures were excluded. Pre-operative non-contrast CT defined stone burden and Guy Stone Score; operative variables, outcomes and complications were extracted from the records and analysed. Results: A total of 124 patients were analysed (supine n = 79; prone n = 45). Baseline age, sex, BMI and ASA classification were similar, but the prone group harboured larger stones (mean surface area 11.04 vs 5.68 cm 2 , p < 0.001) and more Guy stone score 4 cases. Mean operative time was significantly shorter in the supine position (96.9 ± 46.7 min) than in the prone position (159.6 ± 66.7 min; p < 0.001), the difference was most pronounced in Guy stone score 2 and 3 cases. This represents an approximate 63-minute operative time reduction with the supine approach. Stonefree rates (67.1% supine vs 68.9% prone; p = 0.837), overall treatment success (81% vs 73.3%; p = 0.319), transfusion (2.6% vs 8.9%; p = 0.113), complications (p = 0.134) and hospital stay (2.3 ± 1.6 vs 2.6 ± 1.9 days; p = 0.378) were similar. In Guy stone score 4 cases, the prone group showed a non-significant trend toward higher clearance. Conclusion: In obese patients, supine and prone PCNL provide equivalent safety and stoneclearance outcomes. Supine positioning offers a substantial operativetime advantage for low to moderate complexity stones, whereas the prone approach remains a viable option for very large or staghorn calculi when multiple tract access is anticipated.