Nomogram for predicting risk factors of postoperative residual stones in patients after pure ultrasonography-guided access mini-percutaneous nephrolithotomy.

Background: Some urologists prefer to perform PCNL by using pure ultrasonography-guided access (USGA), but some potential factors that may cause the residual stones need to be excavated. This retrospective case-control study is designed to confirm the risk factors for residual stones after pure USGA mini-percutaneous nephrolithotomy (mPCNL) in patients and develop a nomogram for predicting postoperative residual stones based on the risk factors.

Methods: From October 2019 to August 2021, our department recorded a retrospective record of 227 patients with kidney stones treated with pure USGA mPCNL. The risk factors for postoperative residual stones were confirmed by univariate and multivariate logistic regression analysis, and a nomogram was developed. As a result, the nomogram was accessed with discrimination, calibration, and clinical applicability in mind.

Results: The rate of residual stones in patients was 34.4% during the management of USGA mPCNL. The independent risk factors for residual stones were history of ipsilateral PCNL surgery (OR = 3.163, P = 0.020 ), calyx number with stones (OR = 5.628, P = 0.006 ), stone burden (OR = 1.004, P = 0.008 ). Calculated by receiver operating characteristic (ROC) analysis, the area under the curve (AUC) was 0.884 (95% CI 0.829-0.940). The concordance index (C-index) of calibration curves was 0.842, meaning good concordance. The clinical decision curve analysis (DCA) showed a good clinical practicability in clinical practice.

Conclusions: Patients with history of ipsilateral PCNL surgery, calyx number with stones and stone burden may be at increased risk of residual stones. The nomogram can evaluate the risk of residual stones in patients who undergo USGA mPCNL.

Clinical trial number: Not applicable.