Hitmaker Lady Gaga has sent fellow pop star Selena Gomez prayers after the latter's kidney transplant operation.

Gaga tweeted "Prayers & love to @selenagomez you are a warrior princess. What an inspiration," following the "Fetish" singer's revelation that she had a kidney transplant over the summer.

Gomez shared a photo of herself and friend Francia Raisa on Instagram on Sept. 16. The two are seen smiling at each other in the photo while on their own hospital beds. Raisa donated one of her kidneys to Gomez, as the latter's lupus was starting to become more life-threatening.

"There aren't words to describe how I can possibly thank my beautiful friend Francia Raisa," Gomez wrote in the caption. "She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed."

The singer also answered the fans' burning question about why she has not been promoting her new music as much as she used to when she releasing songs.

"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," she wrote. "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."

Gomez encouraged fans to learn more about lupus, which she said is still largely misunderstood.

Lupus is an autoimmune disease that reduces protection for various parts of the body such as the joints, skin, kidneys, heart, lungs, blood vessels and brain, according to the Lupus Research Alliance, which Gomez herself promoted on her Instagram post.

Common symptoms of the disease include extreme fatigue, painful or swollen joints, unexplained fever, skin rashes and kidney problems. There is no cure for the disease yet.