Darren Fletcher is unlucky – about one in 10,000 people develop ulcerative colitis each year. It is a chronic condition causing inflammation of the bowel with symptoms, typically, of abdominal pain, bloody diarrhoea and a frequent need to go to the toilet.
In many cases the symptoms are mild and do not interfere with normal life. But the stress of playing Premier League football will not have helped. The condition is unpredictable and symptoms may flare up and then disappear for months or years.
It tends to run in families with about one in six cases having a relative with the condition. Diet is an important trigger and sufferers have to learn which foods make their symptoms worse. Fatty foods and carbohydrates, the mainstay of the western diet, tend to aggravate the condition. The incidence is lower among Asians who eat more pulses and vegetables.
Eating little and often is the best defence – five or six small meals are better than three large ones. Sufferers should drink plenty to avoid becoming dehydrated as a result of the diarrhoea. Relaxation techniques such as meditation and yoga may also help.
If modifying the diet does not control the condition, treatment with drugs is the best option, including steroids. In more severe cases immunosuppressants may be used – one theory about the condition is that the gut reacts to a viral infection by becoming inflamed and then fails to switch off the immune response when the threat recedes.
In the worst cases surgery may be required to remove a part of the bowel. Fans must hope Fletcher's absence from the field will be enough to return him to health.