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Your Kidneys and How They Work

What Is "Renal Function"?

Your health care team may talk about the work your kidneys do as renal function. If you have two healthy kidneys, you have 100 percent of your renal function. This is more renal function than you really need. Some people are born with only one kidney, and these people are able to lead normal, healthy lives. Many people donate a kidney for transplantation to a family member or friend. Small declines in renal function do not cause a problem. In fact, you can be healthy with 50 percent of your renal function if it remains stable.

But many people with 50 percent of their renal function have a kidney disease that will get worse. You will have some serious health problems if you have less than 20 percent of your renal function. If your renal function drops below 10 to 15 percent, you cannot live long without some form of renal replacement therapy -- either dialysis or transplantation.

Why Do Kidneys Fail?

Most kidney diseases attack the nephrons, causing them to lose their filtering capacity. Damage to the nephrons may happen quickly, often as the result of injury or poisoning. But most kidney diseases destroy the nephrons slowly and silently. It may take years or even decades for the damage to become apparent.

The two most common causes of kidney disease are diabetes and high blood pressure. If your family has a history of any kind of kidney problems, you may be at risk for kidney disease.

Diabetic Nephropathy

Diabetes is a disease that keeps the body from using sugar as it should. If sugar stays in your blood instead of breaking down, it can act like a poison. Damage to the nephrons from unused sugar in the blood is called diabetic nephropathy. If you keep your blood sugar levels down, you can delay or prevent diabetic nephropathy.

High Blood Pressure

High blood pressure can damage the small blood vessels in your kidneys. The damaged vessels cannot filter poisons from your blood as they are supposed to.

Your doctor may prescribe blood pressure medication. A group of blood pressure medicines called ACE inhibitors appears to give extra protection to the kidneys in patients with diabetes.

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