Selena Gomez Gets a Kidney Transplant From Francia Raisa

Just a few months ago, Selena Gomez was seemingly everywhere.

With a new single to promote ("Bad Liar"), she graced the cover of Vogue and did multiple interviews. But then, as the summer went on, the 25-year-old pop star seemingly disappeared.

As Gomez announced via Instagram Thursday, she had a good reason for taking time out of the spotlight.

"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. So I found out I needed to get a kidney transplant due to my Lupus and was recovering. It was what I needed to do for my overall health. I honestly look forward to sharing with you, soon my journey through these past several months as I have always wanted to do with you. Until then I want to publicly thank my family and incredible team of doctors for everything they have done for me prior to and post-surgery. And finally, there aren’t words to describe how I can possibly thank my beautiful friend Francia Raisa. She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed. I love you so much sis. Lupus continues to be very misunderstood but progress is being made. For more information regarding Lupus please go to the Lupus Research Alliance website: www.lupusresearch.org/ "

Gomez, who in 2015 publicly revealed that she is battling Lupus, said she needed a new organ to improve her "overall health." While she didn't want to go into too many details, she wrote, "I honestly look forward to sharing with you, soon my journey through these past several months as I have always wanted to do with you. Until then I want to publicly thank my family and incredible team of doctors for everything they have done for me prior to and post-surgery."

The singer admitted "there aren't enough words" to properly thank her "beautiful friend," 29-year-old Secret Life of the American Teenager star Francia Raisa. "She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed. I love you so much sis," the "Fetish" singer wrote. "Lupus continues to be very misunderstood but progress is being made."

Gomez posted photos of herself in the hospital with Raisa, as well as of her post-surgery scars. The singer ended her note by asking her followers to visit the Lupus Research Alliance website.

Raisa, meanwhile, has yet to public speak about her organ donation.