Methods for calculating the number of nephrons from ultrasound scans and kidney biopsies for nephrologists’ use

The interest in determining the number of nephrons in the kidney dates back to the 1960s, when an influential laboratory method for determining ex vivo the number of nephrons in the kidneys was described by Bricker. Over the years, various methods have been developed to estimate the number of nephrons in living beings as accurately as possible. These modern methods combine data such as the glomerular density, the percentage of glomeruli in sclerosis calculated from biopsy samples, and the kidney volume, which can be precisely estimated from magnetic resonance, CT scan, or specific ultrasound methods. As the reduction in the number of functioning nephrons is closely connected with an increased risk of progression of renal disease (especially in patients with nephrotic syndrome) and hypertension, its introduction into clinical practice could allow a precise stratification of progression risk in patients with kidney disease and a better understanding of the mechanisms that contribute to the loss of functioning nephrons.