CT Stone volume versus Guy’s Stone Score for predicting stone free rate and early complications following single tract percutaneous nephrolithotomy: A prospective cohort study at a tertiary hospital

Objective: To compare computed-tomography (CT) stone volume and Guy’s Stone Score (GSS) as pre-operative predictors of stone-free rate (SFR) and early (≤30-day) complications after single-tract percutaneous nephrolithotomy (PCNL). Methods: This prospective, analytic-observational study was conducted at Dr Soetomo General Hospital, Surabaya, Indonesia, between 1 March 2024 and 30 June 2025. It included 82 adult patients who underwent single tract PCNL. Stone volume was calculated by ellipsoid formula on Synapse 3D®, anatomical complexity was assessed by GSS I-IV, while the primary outcome was stone-free rate (SFR) and secondary outcome was early complications (PCNL-specific Clavien-Dindo). Mann-Whitney U, χ², and Spearman correlation were used for data analysis. Results: Sixty-one patients achieved SFR (74 %). Median stone volume was 4.91 cm³ (IQR 4.19–5.68) in stone-free versus 12.03 cm³ (10.00–13.33) in non-stone-free cases (p < 0.001). Stone volume correlated strongly and inversely with SFR (ρ = –0.75, p<0.001). All GSS I–II cases were stone-free, whereas all GSS III–IV retained fragments, yielding an even stronger inverse correlation (ρ = –0.80, p<0.001). Early complications were limited to Clavien I (18, 22 %) and II (64, 78 %); none ≥III. Complication grade correlated modestly with GSS (ρ = +0.28, p=0.011) and stone volume (ρ = +0.25, p=0.024). Conclusion: GSS remains the most powerful single predictor of stone clearance and minor complications after single-tract PCNL, whereas CT-derived stone volume offers complementary quantitative nuance. Integrating both parameters may refine risk stratification and operative planning in high-volume settings.