Nick Jonas praises 'inspiring' pal Selena Gomez after kidney transplant revelation

Nick Jonas has praised his "inspiring" friend Selena Gomez for going public after having a kidney transplant earlier this year (17).

Selena took to Instagram last week to reveal that she had undergone the operation as part of her ongoing battle with autoimmune disease lupus, and that her best friend Francia Raisa had donated her kidney.

Nick, who dated Selena from 2008 to 2010, was asked if he knew about the surgery during an interview on SiriusXM's Hits 1 radio show, and admitted he had been in the dark until the singer announced it on social media.

"I was just as surprised as everyone else when I woke up and saw her Instagram, but wow -- that's just incredible, and the strength she's shown through all of that is amazing and inspiring," he said.

"I'm pumped for her. I'm happy to see she's doing well, it seems, and she was able to get the surgery, and her friend helping her is a beautiful thing. So it's all amazing."

Nick isn't the only star to praise Selena after the operation; Lady Gaga also showed her support, and tweeted: "Prayers & love to @selenagomez you are a warrior princess. What an inspiration."

Kesha, meanwhile, included Gaga in her tweet to Selena, after the star opened up about her battle against fibromyalgia last week.

"My heart is with selena gomez and lady gaga today," she tweeted. "We're all human & need self care. i hope both these icons heal safe & feel good. such wonderful role models for being so honest with a very critical world."

Selena hit headlines worldwide when she revealed she had undergone the surgery, explaining in a note to fans that the operation was the reason she hadn't been promoting her music over the summer months.

"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 alongside a picture of herself lying in a hospital bed next to her kidney donor and friend Francia.

"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."