A middle-ranking diplomat aged 29 presents with a four week history of lower abdominal pain and diarrhoea. The pain is described as moderate and is generally relieved by defaecation. The diarrhoea is free of blood but half of the stools are liquid; there is now a total stool frequency of eight times in 24 hours, which wakes him from sleep on most nights. He suspects that he has lost weight but has no scales at home, and night sweats have raised the possibility that …