History A 35-year-old woman has a year-long history of intermittent diarrhoea which has never been bad enough for her to seek medical help in the past. However, she has become much worse over 1 week with episodes of bloody diarrhoea 10 times a day

History A 35-year-old woman has a year-long history of intermittent diarrhoea which has never been bad enough for her to seek medical help in the past. However, she has become much worse over 1 week with episodes of bloody diarrhoea 10 times a day. She has had some crampy lower abdominal pain which lasts for 1–2 h and is partially relieved by defecation. Over the last 2–3 days she has become weak with the persistent diarrhoea and her abdomen has become more painful and bloated over the last 24 h. She has no relevant previous medical history. Up to 1 year ago, her bowels were regular. There is no disturbance of micturition or menstruation. In her family history, she thinks one of her maternal aunts may have had bowel problems. She has two children aged 3 and 8 years. They are both well. She travelled to Spain on holiday 6 months ago but has not travelled elsewhere. She smokes 10 cigarettes a day and drinks rarely. She took 2 days of amoxicillin after the diarrhoea began with no improvement or worsening of her bowels.