A dual-sheath approach in minimally invasive percutaneous nephrolithotomy is associated with reduced residual stone risk: a two-center retrospective study

To compare the efficacy and safety of a novel dual-sheath approach (combined metal and peel-away sheath) versus a single peel-away sheath in minimally invasive percutaneous nephrolithotomy (MIPCNL) for complex renal or ureteral calculi, and to identify factors associated with postoperative residual stones. This retrospective two-center study included 211 patients with complex renal or ureteral calculi who underwent MIPCNL between January 2023 and December 2024 (dual-sheath group, n =123; single-sheath group, n =88). All procedures were performed by experienced surgeons following a standardized protocol. Propensity score matching (PSM) was applied to balance baseline characteristics. Cox proportional hazards models were used to identify factors associated with residual stones. Kaplan–Meier analysis with log-rank testing was used to compare cumulative residual stone risk between groups. Baseline characteristics were generally comparable between groups. The dual-sheath group showed a trend toward a higher 4-week stone-free rate compared with the single-sheath group (82.9% vs. 71.6%, P =0.072). The secondary intervention rate was significantly lower in the dual-sheath group (0.81% vs. 12.5%, P <0.001). No significant differences were observed in postoperative complication rates between groups. Cox regression analysis indicated that dual-sheath use was independently associated with a reduced risk of residual stones (HR =0.47, 95% CI: 0.25–0.88, P =0.019), with consistent results across sensitivity models. Kaplan–Meier analysis demonstrated a significantly lower cumulative incidence of residual stones in the dual-sheath group (log-rank P =0.0063). The dual-sheath technique appears to be a feasible and safe modification of MIPCNL for complex renal or ureteral calculi. It is associated with a reduced risk of residual stones and fewer secondary interventions, while a non-significant trend toward improved stone-free rates was observed. Further prospective multicenter studies are needed to confirm these findings.