Singer, Selena Gomez has been sick or a while, as she underwent a kidney transplant this summer, and the donor was her best friend.

Selena posted this post-surgery photo of her and kidney donor, Francia Raisa. She said, "I'm very aware some of my fans had noticed i was laying low for part of the summer and questioning why I wasn't promoting my new music, which I was extremely proud of."

Selena goes on ... "So I found out I need to get a kidney transplant due to my Lupus and was recovering. It was what I needed to do for my overall health."