The Australian claims that doctors found a "dangerous blood clot" and needed to act on it as soon as possible.
The Bee Gees star is recovering from an intestinal operation, with his publicist confirming yesterday that Gibb had pulled out of a number of shows.
Meanwhile, his attendance at the premiere of his classical score The Titanic Requiem on April 10 is still in doubt.
Last November, the 61-year-old confirmed he had been diagnosed with liver cancer, shortly after reports he had cancelled a meeting with British Prime Minister David Cameron due to illness.
However, Gibb revealed earlier this month that he is in remission from the disease, after making his stage comeback in February.
His current condition has not yet been confirmed.
> Robin Gibb: 'Cancer is payback for Bee Gees success'