Percutaneous nephrolithotripsy (PCNL) is currently the predominant treatment modality for renal stones larger than 20 mm. However, due to various multifactorial reasons, a considerable number of cases with residual calculi post-PCNL exist. Nowadays, comprehensive data regarding the characteristics of cases with residual stones following the first PCNL and the supplementary outcomes of salvage PCNL are still inadequate.

This retrospective analysis included 72 patients who underwent salvage percutaneous nephrolithotomy (PCNL) between January 2020 and January 2023 after the initial procedure. Information regarding patient's demographic, characteristics of the calculi, reasons for failure, and outcomes following treatment, including stone-free rates and complications according to the Clavien-Dindo system, were documented for the second-look intervention.

The primary causes of initial procedure failure were prolonged operative time (68.06%), unsuitable target calyx (9.72%), intraoperative infection (11.11%), planned staged procedures (5.56%), and significant hemorrhage (5.56%). Following the salvage PCNL, the overall stone-free rate was 55.41%. Multivariate logistic regression analysis identified the presence of multiple stones (OR = 6.434, p = 0.015) and Guy’s stone score 4 (OR = 11.620, p = 0.01) as independent predictors of persistent residual stones following the second intervention. For postoperative outcomes of second procedures, 80.56% of cases were free from complications, with no reported grade 3B or above events. Performing a second PCNL during the same hospitalization reduced hospital stay duration and antibiotic use compared to procedures conducted during separate admissions.

Patients with residual stones after primary PCNL face anatomical and procedural challenges that impede complete stone clearance. Salvage PCNL yielded a stone-free rate of 55.41%, with multiple calculi and a higher Guy’s stone score increasing the chance of residual fragments. These results highlight the importance of thorough preoperative assessment, customized surgical planning, and intraoperative optimization to improve the effectiveness of secondary PCNL in patients with ongoing nephrolithiasis.