Epidemiology and natural history of inflammatory bowel diseases

In the West, the incidence and prevalence of inflammatory bowel diseases has increased in the past 50 years, up to 8-14/100,000 and 120-200/100,000 persons, respectively, for ulcerative colitis (UC) and 6-15/100,000 and 50-200/100,000 persons, respectively, for Crohn's disease (CD). Studies of migrant populations and populations of developing countries demonstrated a recent, slow increase in the incidence of UC, whereas that of CD remained low, but CD incidence eventually increased to the level of UC. CD and UC are incurable; they begin in young adulthood and continue throughout life. The anatomic evolution of CD has been determined from studies of postoperative recurrence; CD begins with aphthous ulcers that develop into strictures or fistulas. Lesions usually arise in a single digestive segment; this site tends to be stable over time. Strictures and fistulas are more frequent in patients with ileal disease, whereas Crohn's colitis remains uncomplicated for many years. Among patients with CD, intestinal surgery is required for as many as 80% and a permanent stoma required in more than 10%. In patients with UC, the lesions usually remain superficial and extend proximally; colectomy is required for 10%-30% of patients. Prognosis is difficult to determine. The mortality of patients with UC is not greater than that of the population, but patients with CD have greater mortality than the population. It has been proposed that only aggressive therapeutic approaches, based on treatment of early recurrent lesions in asymptomatic individuals, have a significant impact on progression of these chronic diseases.