Impact of preoperative proteinuria on renal functional outcomes after open partial nephrectomy in patients with a solitary kidney

PURPOSE: To assess the impact of proteinuria on postoperative renal function after open partial nephrectomy (OPN) in patients with a solitary kidney and analyze predictive factors for developing chronic kidney disease (CKD) stage IV or higher. MATERIALS AND METHODS: Patients with a solitary kidney who underwent OPN at Tokyo Women's Medical University Hospital between 1986 and 2016 were the subjects of this study. The patients were divided into 2 groups according to the presence of preoperative proteinuria. The development rate of stage IV CKD or higher was analyzed by the Kaplan-Meier method to compare the postoperative renal function of the 2 groups. Multivariate regression analysis was used to demonstrate predictive factors for postoperative CKD progression. RESULTS: A total of 96 patients, including 73 without proteinuria and 23 with proteinuria, were included in this study. Patients with proteinuria were more likely to be men (95.6% vs. 64.3%, p<0.01), had a higher body mass index (25.7 kg/m(2) vs. 23.5 kg/m(2), p<0.01), and had a higher incidence of hypertension (69.5% vs. 39.7%, p=0.01). Patients with proteinuria had a higher probability of developing stage IV CKD or higher (p=0.0002). Lower preoperative eGFR (p<0.0001) and positive proteinuria (p=0.04) were independent predictors for CKD stage progression on multivariate analysis. CONCLUSIONS: Preoperative proteinuria and eGFR were independent predictors for developing stage IV CKD or higher after OPN. Meanwhile, surgical factors including ischaemia time and tumor size had no significant effect. This suggests that assessment of preoperative CKD stage could help stratify patients according to their risk of renal function exacerbation.