The announcement about President Castro’s gastro-intestinal bleed and treatment has been, probably deliberately, vague. Gastro-intestinal bleeding is a common emergency. The first step is to determine the site of the bleeding, upper or lower.

Upper gastro-intestinal bleeding comes from above the junction of the duodenum, the first part of the small intestine, and the jejunum, the intestine’s second section.

Forty per cent of upper gastro-intestinal bleeding is related to acute gastritis, usually the result of stress, alcohol or pain killing drugs; 30 per cent is from duodenal or gastric ulcers; 10 per cent from an acute tear in the lower end of the gullet wall and 8 per cent from varicose veins in the oesophagus or the stomach. This last cause is usually a late result of heavy drinking associated with cirrhosis.

Bleeding from acute gastritis either spontaneously stops or can be arrested by endoscopy (the insertion of a tube via the throat) in 90 per cent of cases.

Bleeding ulcers or varicose veins can also be stopped endoscopically in a majority of cases. Although President Castro’s taste for cigars would predispose him to upper, rather than lower gastro-intestinal bleeding, available information favours the latter diagnosis.

He has had surgery, and as the term "intestinal bleeding" rather than the usual medical description "upper (or lower) gastro intestinal bleeding" was used, it seems likely to stem from a point between the second part of his small intestine and the rectum.

The two most common causes of bleeding from the lower intestinal tract are diverticular haemorrhage or ectasias.

Ectasias are areas in which the blood vessels have become enlarged, tortuous and covered only by the thin lining of the intestinal wall. They rupture easily.

A diverticulum is a weak patch of the gut that has formed a pouch. They frequently become ulcerated and infected. Both ectasias and diverticulosis, multiple diverticula, become increasingly common with age.

As the surgery has been described as delicate and complex it might be supposed that the diagnosis is more complex than either diverticulosis or an ectasia.

Speculation will centre on the possibility of a bleed from a cancer or benign tumour in his colon or small intestine. If bleeding is massive, and the bleeding point can’t be found, the surgeon needs to remove a length of the gut, a blind sub-total colectomy. Mortality is high, up to 16 per cent in young people, up to 50 per cent in those of advanced years.

It is possible that Castro could suffer from ulcerative colitis, proctitis, or Crohn’s disease, but at nearly 80, it is likely he would have shown signs of these conditions earlier.

Although he fainted while making a speech in 2001 and has since suffered orthopaedic injuries suggesting that he has a liability to fall, there is no previous evidence that he was suffering from anything other than hard work.

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