Does Obesity Influence the Outcomes of Supine Mini-Percutaneous Nephrolithotomy? A Retrospective Observational Study

Background and Objectives: The objective of this study is to evaluate the impact of obesity on postoperative outcomes following supine mini-percutaneous nephrolithotomy (mini-PCNL). Materials and Methods: This retrospective observational study included 110 consecutive patients who underwent supine mini-PCNL between October 2024 and March 2026. Patients were stratified into non-obese (BMI < 30 kg/m², n = 59) and obese (BMI ≥ 30 kg/m², n = 51) groups. Preoperative characteristics, stone-related parameters, and perioperative outcomes were compared. The primary endpoint was the 30-day postoperative complication rate according to the modified Clavien-Dindo classification. Secondary outcomes included operative time, hemoglobin drop, stone-free rate (SFR), and postoperative day 1 discharge rate. Results: Obese patients presented with greater cumulative stone diameter and skin-to-stone distance. Operative time was longer in the obese group (45 [40-60] min vs. 35 [30-60] min; p = 0.029). However, after adjustment for cumulative stone diameter and age, obesity was not independently associated with operative time, whereas stone size remained a significant predictor. No significant differences were observed between groups regarding hemoglobin drop (obese cohort: 9.27 ± 8.22 g/L vs. non-obese cohort: 8.88 ± 7.35 g/L; p = 0.95), SFR (obese cohort: 94.1% vs. non-obese cohort: 89.8%; p = 0.41), postoperative day 1 discharge (obese cohort: 86.3% vs. non-obese cohort: 89.8%; p = 0.768), or overall complication rates (obese cohort: 5.88% vs. non-obese cohort: 6.78%; absolute risk difference, -0.9 percentage points; 95% CI, -10.0 to 8.2; p = 1.000). Conclusions: In this cohort, no statistically significant differences were observed between obese and non-obese patients in the assessed perioperative outcomes, except for operative time, which was longer in obese patients, and the observed difference appeared to be largely explained by differences in stone burden in the present cohort. These findings support the feasibility of standardized supine mini-PCNL in obese patients, although larger prospective studies are needed to confirm these results.