A growing body of research suggested a link between nephron number and vulnerability to kidney illness. However, direct measurement of nephron number in a clinical environment was not practicable. Recent clinical investigations had estimated nephron number and single nephron glomerular filtration rate using glomerular density from a single biopsy and total kidney cortical volume from imaging. The accuracy of these estimations from individual participants, however, was uncertain. Furthermore, it was unclear how the size of the sample or the site of the biopsy might affect the estimations. The concerns were crucial for the design of the study as well as the prospective application of the methods to estimate nephron number in individual participants.

The diversity in predicted nephron number resulting from needle or virtual biopsies was assessed, and cortical volume in human kidneys was reduced for transplantation. Researchers took repeated needle biopsies in the same kidney and used magnetic resonance imaging to look at the three-dimensional spatial distribution of nephron density. The accuracy of a single-kidney biopsy in predicting the mean nephron number calculated from numerous biopsies from the same kidney was tested.

A single needle biopsy had a 15% probability and a virtual biopsy had a 60% chance of being within 20% of the whole-kidney nephron number. Single needle biopsies might be utilized to discover changes in nephron number among large cohorts of hundreds of patients.

Natural intra kidney variability in glomerular density could be used to determine the number of individuals needed to reliably identify variations in nephron number between populations. In individual people, a single biopsy is inadequate to correctly estimate nephron quantity.

Reference:jasn.asnjournals.org/content/33/1/39