[Renal aging in man].

Renal morphological and functional changes occur in the elderly. Between the ages of 50 and 80 years the renal mass diminishes by a mean of 20 percent, to the expense of the renal cortex. Glomerular sclerosis results in a gradual fall in the number of functioning glomeruli. Simultaneously, a decrease of about 7 percent in glomerular filtration rate per decade after the age of 40 years and a 10 percent decrease in renal plasma flow per decade, and therefore an increase in filtration fraction, are observed. These haemodynamic abnormalities are accompanied by changes in tubular function, including a delay in renal adjustment to sodium overload, and above all to sodium restriction, together with a decrease in concentrating and, to a lesser extent, diluting capacity. In actual fact, the intensity of glomerular sclerosis varies considerably from one subject to another, and the decrease in glomerular filtration rate is far from being constant. These changes are perhaps not ineluctably associated with aging; they might result from pathological processes that have gone unnoticed.