Surgeon Assessment of Renal Preservation with Partial Nephrectomy Provides Information Comparable to Measurement of Volume Preservation with 3-Dimensional Image Analysis

Abstract

The strongest predictors of renal function after partial nephrectomy are the preoperative glomerular filtration rate and the amount of preserved parenchyma. Measuring volume preservation by 3-dimensional imaging is accurate but time-consuming. Percent functional volume preservation was designed to replace surgeon assessment of volume preservation with a less labor intensive, objective assessment. We compared volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation as predictors of renal function after partial nephrectomy. We calculated volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation in 41 patients with preoperative and postoperative cross-sectional imaging available. Surgeon assessment was validated internally in another 75 patients. Short-term and long-term renal function was assessed with univariate and multivariate linear regression models. Median parenchymal preservation was 85% (range 37% to 105%) by 3-dimensional imaging, 91% (range 51% to 114%) by percent functional preservation and 88% (range 45% to 99%) by surgeon assessment. Each method strongly correlated with nadir glomerular filtration rate (r(2) = 0.75, 0.65 and 0.78) and latest glomerular filtration rate (r(2) = 0.65, 0.66 and 0.67, respectively, each p <0.0001). Univariate analysis revealed that age, preoperative glomerular filtration rate, renal nephrometry score and each assessment were significant predictors of renal function (p <0.05). On multivariate analysis parenchymal preservation was the strongest predictor (p <0.0001). Models using volume preservation with 3-dimensional imaging, percent functional volume preservation and surgeon assessment of volume preservation were statistically similar in the ability to predict the nadir and latest glomerular filtration rates. In an additional validation cohort surgeon assessment remained strongly correlated with nadir glomerular filtration rate (r(2) = 0.74) and latest glomerular filtration rate (r(2) = 0.73, each p <0.0001). Surgeon assessment of volume preservation provides a reliable estimate of renal functional preservation with characteristics comparable to those of more time intensive alternatives. We propose that surgeon assessment of volume preservation should be routinely reported to facilitate analysis of partial nephrectomy outcomes.