4 Questions You Probably Have About Kidney Transplants

Earlier today, Selena Gomez posted an Instagram explaining the reason why she "was laying low for part of the summer": She had a kidney transplant to help with her lupus. Gomez wrote to thank her donor and "beautiful friend Francia Raisa," and to spread awareness about lupus. "Lupus continues to be very misunderstood but progress is being made," Gomez wrote.

Lupus is an autoimmune disease that often harms tissues and organs, specifically a person's heart or kidneys, explains Robert Montgomery, MD, transplant surgeon and director of the Transplant Institute at NYU Langone Health. Around 10 to 30% of people with lupus get a kidney transplant to prevent kidney failure, and they're usually successful.

Typically, a transplant is done once someone is in remission from lupus, and before they need dialysis, Dr. Montgomery says. "You wait as long as you can, and once kidneys are sort of at the end of their functioning, then that's the time you want to get the transplant." If you're curious about the procedure, or you're contemplating donating your own kidney at some point, here's what you need to know:

Your blood type is definitely a big factor, but there are a couple of ways that people can donate and receive transplants with different blood types, Dr. Montgomery says. For example, if you wanted to donate to a friend or family member with a different blood type, you can get paired with another couple (or many other couples) of compatible people, which is called a "swap," he says. (If you're confused, this video does a great job of explaining how the process works.) About 1,000 swaps are performed a year. Or, you could do what's called a "blood-type incompatible transplant," which involves undergoing treatment before the transplant to filter out antibodies that would otherwise make you incompatible, he says.

"For a long time, we only allowed blood relatives to donate to patients," Dr. Montgomery says. But now, people can receive kidneys from "altruistic donors," which are people who offer to donate their kidneys, he says. "Usually, they have some connection with the patient: It can be someone from their church, a friend-of-a-friend, or in [Gomez's] case it was a friend of hers."

In general, kidneys from a live donor tend to last twice as long as a deceased donor. For a young person like Gomez, the kidney needs to be strong, Dr. Montgomery says. "Kidneys aren't like diamonds: They're not forever," he says. "If someone is young, at some point they'll need another kidney, so we want the first one to be the highest quality."

It's important to point out that it's often very difficult for people to receive kidney transplants, depending on their age or where they live. For some people, it can take between three and seven years. If you're interested in becoming an organ donor, check out the United Network for Organ Sharing for more information.

Yes! According to Dr. Montgomery, lots of studies have shown that people live just as long with one kidney as they do with two. And "being a live donor does not affect your long-term life expectancy," he says.

Recovering from a kidney surgery is a lot like recovering from other surgeries, but you also have to get used to having a new kidney inside of you. Recipients usually have to take an immuno-suppressant drug as part of the recovery, and it can take about six weeks. As for the donor? They're also usually back to normal in about six weeks, and are encouraged to have long-term medical follow-up with their primary care physician.