Predictors of Precision of Excision and Reconstruction in Partial Nephrectomy

Purpose: The precision of excision and reconstruction to optimize vascularized parenchymal preservation is a major determinant of renal function after partial nephrectomy. We assessed partial nephrectomy surgical precision using volumetric computerized tomography and analyzed predictive factors. Materials and Methods: We analyzed the records of 122 patients treated with partial nephrectomy in whom detailed analysis of the precision of excision and reconstruction specific to the operated kidney could be performed. We used volumetric computerized tomography to measure functional parenchymal volume before and after partial nephrectomy in the operated kidney. The glomerular filtration rate in the operated kidney was determined by the MDRD2 (Modification of Diet in Renal Disease 2) equation along with renal scan in patients with a contralateral kidney. Surgical precision was defined as actual postoperative parenchymal volume/predicted postoperative parenchymal volume, presuming loss of a 5 mm rim of normal parenchyma related to excision and reconstruction. Results: Median patient age was 61 years and 64 patients (52%) underwent an open procedure. Cold ischemia was used in 50 patients (median 26 minutes) and limited warm ischemia (median 20 minutes) was used in 72. The R.E.N.A.L. (radius, exophytic/endophytic, nearness of tumor to collecting system or sinus, anterior/posterior and location relative to polar line) nephrometry score indicated low, intermediate and high complexity in 43 (35%), 55 (45%) and 24 patients (20%), respectively. A total of 45 patients (37%) with a solitary kidney were included in analysis. The median precision of excision and reconstruction was 93%. The median preserved glomerular filtration rate was 80% in the operated kidney. A solitary kidney was the only significant predictor of excision and reconstruction precision on univariable and multivariable analysis. Conclusions: A solitary kidney significantly impacted partial nephrectomy surgical precision. This was likely related to the recognized need to preserve as much renal parenchyma as possible to optimize renal function in the absence of a contralateral kidney.