Current trends in inflammatory bowel disease: the natural history.

The description of the prognosis of inflammatory bowel disease (IBD) is based on systematic follow-up of population-based cohorts. A steady increase in incidence of IBD has occurred. The distribution of ulcerative colitis (UC) is fairly uniform with a preponderance of left-sided disease. One-third of Crohn's disease (CD) patients present with colonic disease, one-third with ileocolonic disease and one-third with small bowel disease. IBD is associated with extra-intestinal manifestations (EIMs) in up to 36% of patients. Uveitis and episcleritis are the most common. The cumulative probability of a relapsing course in UC is 90% after 25 years. In CD disease behaviour varies substantially with time. At diagnosis behaviour is inflammatory in 70% of patients. At follow-up there is a change to either stricturing or penetrating disease. Most patients with CD will eventually require surgery. Risk factors for CD recurrence after surgery include penetrating/fistulizing disease behaviour, young age, short duration of disease before first surgery and ileocolonic disease. The incidence of colorectal cancer (CRC) in UC seems to be decreasing. The risk of CRC in CD seems to be equivalent to the risk in UC. Patients with small bowel CD are also at increased risk of small bowel adenocarcinoma. CD is associated with a mortality rate 20-70% higher than expected, whereas mortality in UC is equivalent to that of the general population. The improved prognosis of IBD, especially UC, could be due to a chemopreventive effect of the medications used. Further studies are needed to develop the best strategy for the reduction of mortality and cancer risk in IBD.