Insights: What do the kidneys do and why do we have two?
The kidneys are two bean-shaped organs, each about the size of a fist. They are found in your back on either side of the spine. Healthy kidneys have many roles. These include:
Cleaning waste products from the blood by making urine
Balancing the amount of certain elements in your blood (such as sodium, potassium and calcium)
Making hormones that control blood pressure and red blood cells
It is not fully understood why people are born with two kidneys. One theory is that having an extra kidney provides protection in case of injury to one of the kidneys. Another theory is that having two kidneys is part of what is called “bilateral symmetry.” This means humans are the same on both sides. On each side of our body we have an arm, leg, eye, ear, lung and kidney.
People can live with only one kidney. Some people are born with one kidney, or have a kidney removed because of injury or disease. Others donate a kidney to a person who needs a kidney transplant. Most people with one healthy kidney live healthy, normal lives with few problems.
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