Sample size. Power calculation (nQuery Vers, 6.0, Statistical Solutions) showed that assuming a 16% drop-out rate, a common standard deviation of 8.0 ml/min, an equal sample size in each treatment arm, using a two group t-test with a 0.05 2-sided significance level, with 30 patients per arm our study will have a 90% power to detect a difference in means of GFR in the vascularized (or control untreated kidney) of 7.5 ml/min.