An Excerpt from the course on Geriatrics

Renal function

With aging, the kidneys become smaller due to the loss of nephrons, the functional parts of the kidneys.  The loss of nephrons reduces the weight of the kidneys by about one-third of their normal weight. This reduces the surface area available to filter blood.  Change in the arterial system, which supplies blood to the kidneys, also reduces the renal blood flow. These changes result in a lesser amount of blood per minute passing through the kidneys for filtration. Since the kidneys filter out many drugs (including antibiotics), their reduced functioning leads to drug toxicity in older adults if they take too much medication or too frequently.

Structural changes that happen in the renal function with aging:

1. Shrinking of kidneys and decline in glomerular function makes regulating body water, sodium, and potassium, difficult. The functional ability is usually retained until stressed.
2. Decreased renal blood flow increases the risk of toxicity from all drugs and toxins processed in kidneys.