Surgeon said a potential (and exceedingly rare) outcome for a donor is to wake up having gone all the way through the surgery up to the vein, artery and ureter being clipped and having the removal canceled. They don't do the last steps until the recipient is ready to receive the kidney and if something goes wrong for the recipient, they'll cancel the removal for the donor. Could you imagine waking up to that?! I guess the good news(?) is that you can still donate after you heal up. Makes sense though, they're not taking any chances with not being able to use the kidney.