Selena took to Instagram to share the news with her followers in a candid post.
The 25-year-old popstar and actress has suffered from Lupus – a chronic autoimmune disease in which the body’s immune system becomes hyperactive and attacks normal, healthy tissue – since 2015.
The condition led her to take drastic surgery in the summer of 2017, and she has only now told her fans.
She wrote: “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.”
The brunette beauty went on to reveal that it was her best friend who had donated her kidney.
Selena added: “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.”
One wrote: What?!?! Couldn’t tell she was sick.”
Another replied: “Get well soon and Stay strong baby!”
Selena also shared other images, showing off the scars on her body following the operation.