MELBOURNE: World number four Sofia Kenin has undergone emergency surgery to remove her appendix, just days after her Australian Open defence ended in a tearful second-round exit.

The 2020 Australian Open champion consulted a tournament doctor on Monday after suffering acute abdominal pain and sent to hospital.

"Acute appendicitis was diagnosed following the completion of my CT scan," Kenin tweeted.

"I had to have surgery and had my appendix removed on Monday, February 15, at Epworth Hospital Richmond.

"I want to thank everyone at Epworth Hospital Richmond for taking good care of me!"

The American endured a difficult maiden Grand Slam title defence and was knocked out by unseeded Kaia Kanepi 6-3, 6-2 in the second round six days ago.

Kenin, 22, was just the third defending champion not to reach the third round since 1970 and the earliest exit since Jennifer Capriati lost in the first round in 2003.

After her exit, a highly emotional Kenin admitted to being unable to handle the expectations in Melbourne as tears welled up.

Her slump deepened when she was stunned by unranked Australian teenager Olivia Gadecki at the Phillip Island Trophy on Sunday, before Kenin's illness and hospitalisation a day later.