Former St Helens and England full-back Steve Prescott MBE has been admitted to hospital after taking part in a gruelling fund-raising challenge.
The 48-hour Engage Mutual race, in which Prescott swam, ran, cycled and canoed his way from Hull to Manchester in time for last Saturday's Grand Final, left him significantly drained and complaining of severe stomach pains.
Prescott, who was diagnosed with a rare form of abdominal cancer in 2006, was admitted to hospital on Monday evening and will remain there for several more days.
A spokesman for the charity, the Steve Prescott Foundation, said: "Following a series of tests, doctors have established that due to the rigours of the challenge, Steve has lost a substantial amount of natural fuels and fluids, including electrolytes, meaning his bowel is unable to function.
"Doctors have prescribed a range of treatments and, while gradually bringing his fluid levels back to normal, he was also administered a course of morphine to relieve the pain and remained in hospital overnight under observation.
"This morning, Steve is said to be responding well to treatment but will remain in hospital, under medical observation, for the next day or so."
Prescott's fund-raising efforts were in aid of The Christie cancer hospital in Manchester and the Rugby League Benevolent Fund.