Ulcerative colitis is the most common inflammatory disease of the bowel, followed by Crohn’s disease.1
It is associated with significant morbidity and may have significant psychological sequelae. It has an incidence of 10 per 100,000 people annually in the UK, with a prevalence of 240 per 100,000 people.1
It can affect all age groups, but there is a peak at 15-25 years and a further, smaller peak at 55-65 years.1
The condition is idiopathic but there may be a genetic susceptibility and there may be an immunomodulatory component. Interestingly, smoking is associated with milder disease and removal of an inflamed appendix in early life reduces the incidence of ulcerative colitis.2
In ulcerative colitis the extent of the disease is continuous, with diffuse inflammation of the colonic mucosa.1 This is in contrast to Crohn’s disease, where skip lesions may be present.
Rectal involvement is referred to as proctitis and if the disease also involves the sigmoid colon, this is referred to as proctosigmoiditis. If colitis is described as extensive, this means that ulcerative colitis is affecting the colon proximal to the splenic flexure.1