Affects about one in every 650 people in the UK and is increasing in incidence.
Inflammation can affect any area of the GI tract from the mouth to the perianal area. Upper GI Crohn's disease is more common in children, affecting around 10% of patients, but much rarer in adults (thought to be about 1%).
Inflammation can be transmural and skip lesions can be present. Crohn's can be further complicated by fistulating or stricturing disease.
Perianal disease, small-bowel disease or fistulas are features of Crohn's and not seen in ulcerative colitis.
Inflammation is limited to the rectum and colon and occasionally the terminal ileum, and confined to the mucosa.
Inflammation is always continuous from the rectum (unless partially treated).
Bloody diarrhoea is more common in UC.
UC may be difficult to distinguish from infective causes of diarrhoea, but often a history of chronicity will help to differentiate the two.
Abdominal pain is not a common presenting feature of UC.