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The kidneys: how they work and what happens when they don’t

Kidneys are important organs responsible for regulating many body processes. They eliminate waste from normal metabolic processes, regulate fluid and electrolyte balance like potassium, calcium and phosphorus, and regulate blood pressure and red blood cell production. But having two kidneys is really more than a body needs.

“It’s a redundant system,” says Miguel Tan, M.D., a transplant surgeon at Piedmont Transplant Institute. “It’s like having an appendix. It’s there, but no one knows what it does. You can survive very well on a single kidney.”

With two kidneys, your body is at 100 percent function. Once you donate a kidney or lose a kidney for whatever reason, you’re at 60 to 65 percent function. But to function normally, you only need 30 percent function.

“We don’t start considering people for kidney transplantation until they get to 20 percent and below,” says Dr. Tan. “So with 60 percent function, you’re perfectly normal. It just means you don’t have as much reserve as you would. So there are things you have to look out for as far as diet and medications.”

Symptoms of kidney failure

Dr. Tan says, generally speaking, if one kidney is failing the other is failing, too, unless it’s for some mechanical reason. Some common signs and symptoms include fatigue, itching and fluid retention.

Sometimes, the first thing people will notice is peripheral edema, or fluid in their legs, as well as difficulty breathing because they develop congestive heart failure.

Kidney failure and dialysis

The quality of life once a patient’s kidneys fail and he or she goes on dialysis is generally fairly poor, Dr. Tan says.

“Their lifestyle tends to take a big hit because, once on dialysis, they’re basically tied to going to hemodialysis for several hours, three times a week. Most people feel wiped out and fatigued afterward. Even people who are on peritoneal dialysis at home are tied to the machine and have to do it daily.”

Aside from the lifestyle limitations of being on dialysis, having kidney disease has an effect on how long you live. If you’re a diabetic and on dialysis, at five years, your chances of dying are almost 40 to 50 percent, compared to someone who gets a transplant or does not have kidney disease, Dr. Tan says.

Facts about the kidneys

Kidney facts:

  • The kidney is about the size of a human fist and weighs about five ounces (150 grams).

  • Kidneys eliminate waste from normal metabolic processes; regulate fluid and electrolyte balance like potassium, calcium and phosphorus; and regulate blood pressure and red blood cell production.

  • More than 200,000 people in the U.S. use dialysis on an ongoing basis.

  • Hemodialysis uses a special type of filter to remove excess waste products and water from the body.

To learn more about kidney disease and living kidney donation, visit the Piedmont Transplant Institute.

Need to make an appointment with a Piedmont physician? Save time, book online.

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