Karen Yeates MD,
Vanita Jassal MB, MSc, MD (UK)

It is well known that, with increasing age, physiologic and anatomic changes occur in the human kidney. However, in the geriatric patient it is not always easy to distinguish "normal" age associated changes from abnormalities in renal function. It is important for clinicians to recognize reduced renal function in their patient because of important implications for both its management and treatment. This review aims to answer three questions:

1. What is considered normal versus abnormal in the aged kidney?
2. How can we predict which patients are at risk of decline?
3. Who should be referred for further work up?

Anatomically, many age-related changes are believed to occur simultaneously in the kidney. Most striking is the reduction in the size of the kidney and in the number of nephrons. This decrease is reflected in the decrease in kidney size from roughly 250g at age 60, to 190g at age 80.^1,2 Age-related changes in the renal vasculature are responsible for most of the decrease in nephron mass. These changes occur independently of hypertension, and include sclerosis in the walls of larger renal vessels and further increases in the presence of hypertension.³

Functionally, there is a reduction in renal plasma flow of approximately 10% per decade, from 600ml/min in young adults, to 300ml/min by age 80 years.