The former One Direction singer, 30, was rushed to hospital last week after experiencing “agonising pain” while in Lake Como, Italy, where he was celebrating his one-year anniversary with girlfriend Kate Cassidy.
He was admitted and expected to remain there for several days to undergo urgent tests.
It comes weeks after he told fans that he’d had to postpone his first solo tour after being hospitalised with a serious kidney infection.
Singer Tweedy, 40, and Payne first started dating in 2016. They welcomed their son together in March 2017 and more than a year later announced their breakup in June 2018.
She is said to have been left “upset” upon learning of the Strip That Down hit-maker’s latest scare.
A source told OK!: “Cheryl is a strong person, she’s very kind and she just wants Liam to be happy and healthy. She’s always tried to support him because he’s Bear’s father and she’s always tried to be there for him.”
Adding: “It’s very hard for Cheryl – she feels upset about it. She is worried and concerned for Liam because he’s Bear’s dad and she wants him to be the best dad he can be.”
Payne’s mum Karen has also been “worried sick” about her son’s condition. “It’s so horrible – him being all the way over there,” she told the MailOnline.
Adding: “It’s such a horrible situation and we just hope he’s in the best place possible.”