Statistical analysis
Statistical analyses were performed using IBM SPSS Statistics for Windows, version 20.0. (IBM Inc., Armonk, N, USA). The statistical level of significance for all tests was p <0.05. To evaluate the changes in the measurements obtained at different time points, repeated measures analysis was adopted, and the LSD test was used for multiple comparisons. The Bonferroni-adjusted Student’s t-test was used to assess whether there was a difference between the PN and RN groups for each repeated measurement. Logistic regression analysis was performed to determine significant risk factors, and renal function decline was defined as the decrease between the baseline value and that obtained in the 3rd postoperative year. In univariate analysis, overall survival (OS) was calculated by the Kaplan-Meier method, and the log-rank test was performed. Cox regression analysis was performed to identify significant prognostic factors. Variables significant at the p <0.2 level in univariate analysis and variables considered clinically significant were entered into the Cox regression analysis.