"Initially Owain had a stomach bug and he had those symptoms for around 36 hours. He was starting to improve, but on Tuesday morning his stomach pain became a lot worse," said Team Sky doctor Neil Heron.
Heron continued: "We began to suspect appendicitis and he was taken to Royal Adelaide Hospital where they confirmed the suspected diagnosis.
"The earliest he will leave the hospital is Thursday and recovery and recuperation is likely to take at least four weeks. Owain is obviously disappointed, but he appreciates he needs to be 100% fit to get back racing."
After having the operation, Doull took to Instagram to post a message to fans as he recovered in a hospital bed.
"Not exactly how I pictured making my WorldTour debut," Doull wrote. "But when your appendix ruptures there isn't much you can do."
However the Welshman will now be out of action until late February, with a possible return to racing at the Abu Dhabi Tour.
Thank you for reading 20 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1