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Most people have two kidneys, but some only have one. There are three main reasons why this could be:

1. A person is born with only one kidney.

   • About one in 750 people is born with only one kidney. The medical term for this condition, which is more common in men than women, is renal agenesis. Usually it’s the left kidney that is missing. Because it is possible to be healthy with one kidney, some people don’t find out they have one missing until it’s discovered on an X-ray or sonogram. (In another condition called renal dysplasia, the second kidney is present but does not function properly.)

2. A kidney has been removed due to health problems.

   • A nephrectomy — the surgical removal of a kidney — can be necessary if a kidney has been damaged by cancer or another disease, or injured in an accident.

3. A person donates a kidney.

   • Every year, thousands of people donate one of their kidneys to someone in need of a healthy one. The recipient is often a blood relative or someone who’s close to the donor, such as a spouse or friend. Approximately 87,000 kidneys from living donors were donated from 1988-2008.

What precautions should people take if they have one kidney?

Much of the advice that applies to living with one kidney goes for everybody: eat right, exercise, sustain a healthy weight, stay hydrated and get regular doctor checkups. However, there are special precautions that should be taken by someone living with a single kidney:

• Blood pressure - People with one kidney may be at risk for high blood pressure. They should check their blood pressure frequently and consult a doctor about how to keep it under control. Telling the doctor that they only have one kidney before starting any blood pressure medication is important, because some drugs are more kidney-friendly than others.

• GFR efficiency - The glomerular filtration rate (GFR) measures how well the kidney(s) remove waste from the bloodstream. This rate should be monitored to make sure the single kidney is functioning properly. A doctor calculates the GFR with a formula that takes into account a person’s age, gender and serum creatinine, a measurement of waste in the blood due to muscle cell turnover. Once GFR is calculated, the patient finds out whether they have kidney disease and if so what stage it is at, and can take the necessary precautions to keep the kidney as healthy as possible.

• Protein intake - Proteinuria is a condition in which too much protein leaks from the blood into the urine. People living with one kidney can be susceptible to proteinuria. If an excess of protein is being lost from the blood, the body will retain fluid and sodium, causing swelling in the ankles or abdomen. In order to prevent or treat proteinuria, people should talk to their doctor about whether or not they need to reduce the protein in their diet.

• Participating in contact sports - When only one kidney is present, it often becomes enlarged from the increased work it does. Studies have shown that a single kidney can do as much as 40% more work than when it’s part of a pair. Protecting a single kidney is essential. Consult with a doctor before engaging in sports or activities that could result in injury to the lone kidney. The doctor may suggest wearing equipment to protect the kidney, or advise which sports to play and which ones to avoid.

What happens if the kidney starts to fail?

Symptoms of kidney failure include:

• Swelling in the face or ankles
• Changes in urine frequency/color or a foamy appearance
• Nausea or vomiting
• Changes in the taste of food
• Numbness in the fingers or toes
• Fatigue or exhaustion

Someone who experiences such symptoms must visit a doctor. If kidney function is failing and a person develops end stage renal disease (ESRD), there are two options: dialysis and kidney transplant. There are many types of dialysis to choose from, including in-center hemodialysis, home hemodialysis (HHD), peritoneal dialysis (PD) and in-center nocturnal hemodialysis. The patient and doctor should discuss which is best for the patient’s lifestyle. Even patients who opt for a kidney transplant may have to go on dialysis while waiting for a match.

Summary

Many people with one kidney can live essentially the same as those with two. The remaining kidney is often able to compensate for its missing counterpart. As long as such people eat sensibly, get plenty of exercise, monitor their blood pressure and receive regular checkups, they can expect to lead a healthy life with only one kidney. Even if the lone kidney stops functioning, treatment options are available.