Spherical cap surface model: A novel method for predicting renal function after partial nephrectomy

Abstract

Objectives: To estimate the percent functional volume preservation from preoperative images using a novel method, the spherical cap surface model, and to investigate whether this model can preoperatively predict renal function after partial nephrectomy. Methods: A total of 233 patients with renal cell carcinoma who underwent open or laparoscopic partial nephrectomy between January 2011 and December 2013 were included in the present study. The spherical cap surface model was used to calculate the estimated percent functional volume preservation on preoperative computed tomography, and the estimated percent functional volume preservation was multiplied by the preoperative estimated glomerular filtration rate to predict the postoperative estimated glomerular filtration rate. The occurrence of acute kidney injury also served as an outcome. Univariate and multivariate linear regression, and receiver operating characteristic curve analysis were used to test the model. Results: The estimated percent functional volume preservation calculated by the novel model was significantly associated with both nadir percent estimated glomerular filtration rate preservation and late percent estimated glomerular filtration rate preservation in the multivariate analysis (the P-values were 0.021 and 0.043, respectively). Receiver operating characteristic curve analysis for predicting acute kidney injury after partial nephrectomy showed that volume preservation (P < 0.001) and warm ischemia time (P = 0.040) were both significant. Regarding the ability to predict a significant decrease in late renal function after partial nephrectomy, only volume preservation (P = 0.044) was significant. Conclusions: Preservation of functional volume is the primary determinant of functional outcomes after partial nephrectomy. The spherical cap surface model seems to represent a promising tool to predict nadir and late postoperative renal function in patients undergoing partial nephrectomy.