EDUCATIONAL REVIEW Safety in glomerular numbers

Abstract A low nephron number is, according to Brenner’s hyperfiltration hypothesis, associated with hypertension, glomerular damage and proteinuria, and starts a vicious cycle that ends in renal failure over the long term. Nephron endowment is set during foetal life, and there is no forma-tion of nephrons after 34–36 weeks of gestation, indicating that many factors before that time-point may have an impact on kidney development and reduce nephron numbers. Such factors include maternal malnutrition, stress, diseases, such as diabetes, uteroplacental insufficiency, maternal and neo-natal drugs and premature birth. However, other congenital anomalies, such as renal hypoplasia, unilateral renal agene-sis or multicystic dysplastic kidney, may also lead to a reduced nephron endowment, with an increased risk for hypertension, renal dysfunction and the need for renal replacement therapy. This review focusses on the causes and consequences of a low nephron endowment and will illustrate why there is safety in glomerular numbers