Figure 1.

Method used to estimate nephron number. The retained kidney cortex (red) on the pre-nephrectomy imaging study was segmented to determine cortical volume. The biopsy of the removed kidney was used to calculate volumetric non-sclerotic glomerular density. This included corrections for missing tufts (empty glomerular capsule), and in donors, absence of kidney capsule on the biopsy section. The glomerular density was divided by correction factors to account for our new estimate of tissue shrinkage with FFPE and for volume shrinkage due to loss of perfusion pressure.⁸ Then this “true” glomerular density was multiplied by cortical volume to estimate nephron number. Figure 1 can be viewed in color online at www.jasn.org.