Association between warm ischemia time and renal parenchymal atrophy after partial nephrectomy.

PURPOSE Renal parenchymal volume decrease after partial nephrectomy is associated with late functional outcomes. We examined the relative effects of resection related and atrophy related volume change on late kidney function. MATERIALS AND METHODS Data were analyzed from a cohort of 187 patients who underwent open, laparoscopic or robotic partial nephrectomy between 2009 and 2011. Total change in kidney size after surgery was expressed as percent functional volume preservation measured using the cylindrical volume ratio method. Renal atrophy was expressed as parenchymal thickness preservation, and was assessed by measuring parenchymal thickness before and after partial nephrectomy in regions of the operated kidney distant from the site of resection. Standard statistical analyses were conducted to assess relationships among variables. RESULTS Mean (± SD) percent functional volume preservation was 92% (± 8%), which correlated with a late percent glomerular filtration rate preservation of 91% (± 12%). Mean parenchymal thickness preservation for the cohort was 99% (± 4%). Minimal atrophy was observed in patients with warm ischemia time less than 40 minutes (parenchymal thickness preservation range 98% to 100%). Atrophy was more pronounced in patients with warm ischemia time greater than 40 minutes (parenchymal thickness preservation 96%). Multivariate regression analysis showed correlation of percent functional volume preservation with atrophy; correlation of warm ischemia time, diameter-axial-polar nephrometry score and atrophy with percent functional volume preservation; and correlation of Charlson score and diameter-axial-polar nephrometry score with percent decrease in glomerular filtration rate. CONCLUSIONS In most patients with warm ischemia time less than 40 minutes the incidence of parenchymal atrophy was minimal, suggesting that the kidney volume decrease after partial nephrectomy was predominantly resection related. Kidney volume decrease after partial nephrectomy in patients with warm ischemia time greater than 40 minutes appeared to be due to a combination of resection related and atrophy related changes.