Mr Castro’s Spanish surgeon, José Luis García Sabrido, dismissed the report, saying that any information that did not come from his medical team was “without foundation”. However, the first highly detailed report on Mr Castro’s health added to a growing conviction that, even if he survives, Mr Castro will not be able to resume power, as Cuban officials insist.

El País newspaper said the Cuban leader is suffering from diverticulitis, a severe inflammation of the large intestine, which can lead to severe bleeding and infections and prove highly dangerous for older patients. In the case of Mr Castro, who is 80, the condition has been aggravated by peritonitis, the swelling of the membrane that covers the digestive organs, the newspaper said.

According to the report, Mr García Sabrido first operated last summer to bypass the affected part of Mr Castro’s intestine. However, the operation “did not go well,” the report said. “The link broke and his abdomen was flooded with faeces, causing another peritonitis.”

Mr Castro also failed to heal properly from a second operation to drain his abdomen and bypass his intestine entirely. A bile duct then became infected, a highly serious situation with an 80 per cent mortality rate, the report said.

A prosthesis made in South Korea was reportedly implanted but failed. A replacement from Spain then had to be fitted. The report also said that Mr Castro was being fed intravenously because he was unable to retain nutrients due to an abdominal wound.

The world has been baffled by the Cuban leader’s condition, which he declared a “state secret” on July 31, when he handed power temporarily to his brother, Raúl Castro. John Negroponte, the outgoing US National Intelligence Director, had speculated that Mr Castro was suffering from cancer. But Mr Castro’s surgeon has ruled out that diagnosis, while refusing to shed any more light on his condition.

El País said that it had spoken to two people from the Gregorio Marañon hospital in Madrid where Mr García Sabrido works as the head of surgery. Mr García Sabrido denied being the source for the story and said that he stood by an earlier statement that Mr Castro was recovering “fantastically well”.

Mr Castro himself has been far more circumspect. “Concerning my recovery, I always said it would be a long process,” he wrote in a new year’s message to the Cuban people. “But it is far from being a lost battle.” The airing of his medical details will be a highly unwelcome development for Mr Castro, who has carefully cultivated an image of invincibility for more than 50 years. It is also embarrassing that the Cuban leader has been forced to turn to a European doctor for help. Cuba’s “world-class” health system has for years been the principal selling-point of the revolution.

With Fidel Castro in hospital, Cuba has been ruled so far by his younger brother, Raúl, in a low-key, collegial manner — the antithesis of Fidel Castro. The 75-year-old head of the armed forces has made few public appearances and delegated tasks to other Communist Party officials.

He has also appeared to soften the Cuban Government’s stance on the US. He has raised the prospect of talks with the island’s perennial enemy and hosted the largest delegation of US congressmen since 1959. Many analysts believe he will move to follow China or Vietnam’s example, gradually opening up Cuba’s economy while retaining strict political control.

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