Contralateral kidney volume change as a consequence of ipsilateral parenchymal atrophy promotes overall renal function recovery after partial nephrectomy.

Purpose: To evaluate whether ischemic time is related to ipsilateral parenchymal atrophy (IPA) and contralateral compensational hypertrophy (CCH) and how CCH affects late functional outcome after partial nephrectomy.
Methods: Parenchymal kidney volumes and glomerular filtration rate (GFR) were determined preoperatively and at 3, 6, and 12 months postoperatively in 79 patients. Kidney volume was measured by Voxel Plus® 2.5 with a tissue segmentation tool. Correlation analysis and univariate and multivariate regression models were used to evaluate the recovery of IPA, CCH, and GFR.
Results: The mean preserved ipsilateral kidney volume was 86.7%. At 12 months, mean IPA and CCH were 3.0 and 4.8%, respectively, and the mean GFR decrease was 8.0%. Ipsilateral volume decrease and contralateral volume increase were significant until 6 months postoperatively (p<0.05, for each). IPA and CCH were greater with a longer ischemic time (>35 min; p=0.029 and 0.003, respectively), and CCH correlated positively with IPA (r2=0.052, p=0.045). On multivariate analysis, IPA correlated with a longer ischemic time and percent of preserved normal parenchymal volume (PPV), and CCH correlated with a longer ischemic time, IPA, PPV, and total parenchymal volume increase. At 12 months postoperatively, CCH correlated with GFR recovery (r2=0.072, p=0.026), and significant predictors of GFR recovery were age, sex, PPV, and CCH.
Conclusions: We present the meaningful possibility that longer ischemic time and less preservation of normal parenchyma cause greater parenchymal atrophy, thereby promoting CCH, which contributes to renal function recovery after partial nephrectomy.