Selena posted this pic post-surgery 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."

And then she thanks her friend ... "There aren't words to describe how I can possibly thank my beautiful friend Francia Raisa. She gave me the ultimate gift."