Aging is a time-dependent process affecting all organs and tissues in the human body. The process of aging in the kidney is characterized by structural and functional changes, of which the main feature is a reduction in size, a decreased number of functioning glomeruli, and vascular changes. These changes result in functional deterioration, mainly involving a decrease in renal blood flow and the glomerular filtration rate. Additionally, impaired regulation of electrolyte and water homeostasis due to structural changes in the tubulo-interstitial system can occur. A reduced glomerular filtration rate does not necessarily result in serious clinical complications, and other selected parameters of kidney function may remain within reference value ranges in the elderly. Aging is also accompanied by decreased perfusion of other organs, including the heart and brain, which can induce more serious conditions in the elderly, including cardiac insufficiency or impairment of mental function. Thus, the decrease in renal blood flow in the aging kidney could be regarded as a compensatory mechanism to maintain perfusion of other organs and therefore, it could be also treated as being a beneficial reordering of blood-flow allocation.

Keywords: Aging, Glomerular Filtration Rate, Kidney Function Tests, Renal Circulation