BACKGROUND
The kidneys filter the blood. Wastes are removed and excess fluid is disposed of as urine. The kidneys also play an important role in the chemical balance of the body. As with other organs, kidney function may be slightly reduced with aging.

The urinary system 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 kidney ages, the number of filtering units (nephrons) is reduced. Nephrons filter waste material from the blood.

In addition to this filtering tissue, the overall amount of kidney tissue is reduced. The blood vessels supplying the kidney can become hardened. The kidneys filter blood more slowly.

The bladder wall changes with age. The elastic tissue is replaced with tough fibrous tissue, and the bladder becomes less "stretchy" (distensible). Muscles weaken, and the bladder may not empty completely when going to the bathroom.

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.

EFFECT OF CHANGES

The kidneys have a built-in extra capacity. 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.

RELATED TOPICS

• Aging changes in organs, tissues, and cells
• Aging changes in the bones, muscles, and joints
• Aging changes in the female reproductive system
• Aging changes in the male reproductive system
• Prostate cancer
• Urinary incontinence