Kidney transplant experiences and advice

Is there any way a donated kidney could be returned to the donor if the recipient ends up rejecting it?

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Why though?

Once a kidney is out, it’s basically dead meat. Your immune system just starts tearing it apart.

How long have you guys been on the waiting list?
What kind of medical records or test results do I actually need to pull together to get added to the list?

A close friend of mine was diagnosed with leukemia about four years ago. He actually beat it, which was incredible, but now he’s facing a kidney transplant. Until he can get a transplant, he’s stuck going to dialysis on a regular basis.
He mentioned that he already put his name on waiting lists in both Mexico and France, but he’s worried his chances are slim because his blood type is O+...

I don't know the first thing about how organ donation works, so if anyone could point me toward some helpful advice or resources, I’d really appreciate it so I can pass it along to him. For instance, are there other places where he could register on a donor list? Is there such a thing as an international organ donor registry or something similar? Any bit of information would be useful...