Nephrometry score is associated with volume loss and functional recovery after partial nephrectomy

Purpose: Functional volume preservation after partial nephrectomy is a primary determinant of kidney function. We identified tumor features, including R.E.N.A.L. (radius for tumor size as maximal diameter, exophytic/endophytic tumor properties, nearness of deepest portion of tumor to collecting system or sinus, anterior/posterior descriptor and location relative to polar line) and centrality index nephrometry scores, associated with volume loss after partial nephrectomy. Materials and Methods: A chart and imaging review was done for 237 patients who underwent partial nephrectomy from 2007 to 2010 and met study inclusion criteria. R.E.N.A.L. and centrality index nephrometry scores were measured in all patients. Percent functional volume preservation was estimated a median of 1.4 years after surgery using the cylindrical volume ratio method. Statistical analysis was done to study associations. Results: Independent tumor features associated with percent functional volume preservation included tumor diameter (p <0.001) and the distance from tumor periphery to kidney center (p = 0.02). R.E.N.A.L. and centrality index scores were associated with percent functional volume preservation (each p <0.001). Nephrometry scores were also associated with nadir and late percent glomerular filtration rate preservation. Tumors classified as highly complex, with a centrality index score of 1.5 or less and a R.E.N.A.L. score of 10 or greater, were associated with an average 28% to 30% functional parenchymal volume loss of operated kidneys. A mean 8% difference in percent functional volume preservation was observed among low, intermediate and high tumor complexity categories for R.E.N.A.L. and centrality index scores. Conclusions: R.E.N.A.L. and centrality index nephrometry scores were associated with changes in the percent functional volume preservation and the perioperative functional decrease. Nephrometry scores performed better than diameter alone on statistical analysis. Nephrometry scores may be useful to estimate the likelihood of operative volume loss and by proxy the functional outcome.