Postoperative renal function in patients undergoing unilateral nephrectomy: development of a prediction model using preoperative risk factors and 51Cr-EDTA clearance.

Objectives: To analyze the preoperative variables associated to the postoperative glomerular filtration rate (GFR) outcomes after nephrectomy for benign and malignant conditions, measured by the reference isotopic technique Cr-51-ethylene diamine tetra-acetic (Cr-51-EDTA) and to create a model to predict the short-term postoperative GFR. Secondary aim was to evaluate which of the common equations for GFR estimation (Cockcroft-Gault, Modification of Diet in Renal Disease [MDRD] or Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) has the best correlation with the Cr-51-EDTA. Methods: Patients undergoing unilateral nephrectomy from 2014 to 2018 were selected. Pre- and postoperative variables were prospectively collected. Univariate and multivariate analyses were done to identify independent risk factors associated with renal function outcomes and to create a model to predict the postoperative GFR. Correlation analyses were performed to evaluate the performance of various serum creatinine-based equations for GFR estimation compared with Cr-51-EDTA. Results: In total, 107 patients were evaluated. After univariate and multivariate analyses, older age (p = 0.008), higher split function of the operated kidney on dimercaptosuccinic acid (DMSA) scintigraphy (p < 0.001), and lower preoperative Cr-51-EDTA (p < 0.001) were independent risk factors for higher GFR decline. Correlation analyses showed that GFR estimated by CKD-EPI equation had the best concordance to GFR measured by Cr-51-EDTA. Conclusions: Based on our findings age, DMSA and lower preoperative Cr-51-EDTA are predictors of postoperative renal function after unilateral nephrectomy. For the assessment of estimated GFR, CKD-EPI equation appears to have the best concordance with Cr-51-EDTA.