Q: Why can people survive with just one kidney?

A: The kidneys are fist-size organs that filter waste from about 200 quarts of blood per day, produce urine, regulate the balance of fluid and electrolytes in the body, release hormones that control blood pressure and red blood cell production, and manufacture vitamin D for the body. Perhaps because they’re so critical, our two kidneys together create a highly redundant system capable of doing much more than it needs to.

Joseph Bonventre, chief of the Renal Division at Brigham and Women’s Hospital, says that when healthy adults donate a kidney to a patient who needs a transplant, “there’s plenty of function left in the other kidney to meet demands.” Full story for BostonGlobe.com subscribers.

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