Selena Gomez's best friend and kidney donor Francia Raisa has revealed the singer "could have died" due to complications following the transplant operation last summer.
Raisa donated the organ to Gomez, who suffers from lupus, last year.
The actress, who stars in US TV comedy Grown-ish, told W magazine: "Recovery was hard… Selena did have a complication, too. A few hours after our surgery, I woke up and had a text from her that said 'I'm really scared'.
"My kidney was very active, and when it turned I broke an artery. They had to take her into emergency surgery and get a vein from her leg and build a new artery to keep my kidney in place. She could have died."
The "flipped" kidney caused Gomez to endure six hours of surgery for a procedure that normally takes two to three hours.
Raisa said the pair initially kept news of the operation secret, adding "We didn't want to tell anybody because recovery was very hard for us, and we went through a depression at the time."
She explained that she decided to donate after Gomez broke down while they lived together: "She was asking me about my day and she grabbed a water bottle out of the fridge and tried to open it and couldn't.
"Then she threw it on the floor, and she fell to the floor and started crying. I was like 'What is wrong with you?'
"She said 'I need a new kidney. I don't know what I'm going to do, the wait list is seven to 10 years.' And it just came out of me."
It turned out Raisa was a match and they underwent surgery last summer.
Their operation was made public in an Instagram post, in which they were seen holding hands in separate hospital beds.
Raisa admitted recovery from the transplant was difficult – and that she was in a lot of pain when she went to audition for the role of Ana in Grown-ish two weeks after the op.
More from Entertainment
The show has been a critical and commercial success since its launch in January.
Gomez's career is back on track, too. As well as releasing several hit singles since her surgery, the 25-year-old has also re-kindled her romance with Justin Bieber.