BACKGROUND

The kidneys filter the blood and help remove waste and extra fluid from the body. The kidneys also play an important role in controlling the chemical balance of the body. As with other organs, kidney function may be slightly reduced with aging.

The kidneys are part of the urinary system, which also includes the ureters and the bladder. Bladder control can be affected by muscle changes and changes in the reproductive system.

AGING CHANGES

As the kidneys age, the number of filtering units (nephrons) is reduced. Nephrons filter waste material from the blood. The overall amount of kidney tissue also decreases. The blood vessels supplying the kidney can become hardened, and the kidneys filter blood more slowly.

The bladder wall changes with age. The elastic tissue becomes tough, and the bladder becomes less stretchy. Muscles weaken, and the bladder may not empty completely when urinating.

In men, the urethra may become blocked by an enlarged prostate gland. In women, weakened muscles can allow the bladder or vagina to fall out of position (prolapse), which can block the urethra.

EFFECTS OF CHANGES

Under usual conditions, kidney function remains normal in an aging person, although sometimes they function more slowly than the kidneys of a younger person.

However, decreased efficiency occurs when the kidneys are under an increased workload. Illness, medications, and other conditions can increase kidney workload.

The changes in the kidneys may affect an elderly person's ability to concentrate urine and hold onto water. The response to changes in fluids and electrolytes taken in is slowed. Dehydration occurs more readily because older people frequently have less of a sense of thirst.

Dehydration can also be aggravated if an older person reduces fluid intake in an attempt to reduce bladder control problems (urinary incontinence).

COMMON PROBLEMS

Aging increases the risk for urinary disorders including acute kidney failure and chronic kidney failure. Bladder infections and other urinary tract infections are more common in the elderly. In part, this is related to incomplete emptying. It is also related to changes in the chemical balance of the urinary membranes.

Urinary retention (inability to completely drain the bladder, which can back up into the kidneys and damage them) is more common in the elderly. Many older people experience problems with bladder control (urinary incontinence).

Urinary system cancers are more common in the elderly, especially prostate cancer (men) and bladder cancer.

In both men and women, urinary changes are closely related to changes in the reproductive system. For example, men may experience problems because of an enlarged prostate (benign prostatic hypertrophy). Women may experience vaginal infections (vaginitis) and subsequent bladder infections.

See also:

• Aging changes in organs, tissues, and cells
• Aging changes in the bones, muscles, and joints
• Aging changes in the male reproductive system