Epidemiologic features of acute appendicitis in Ontario, Canada.

INTRODUCTION: To describe the epidemiology of acute appendicitis in the Province of Ontario, we carried out a retrospective population-based cohort study of all patients with acute appendicitis.
METHODS: Using hospital discharge abstracts of patients with acute appendicitis from all acute care hospitals in Ontario for the fiscal years 1991-1998 coded for the Canadian Institute for Health Information, we studied the demographic features, particularly age and sex, length of hospital stay (LOS), incidence, and seasonal variation of acute appendicitis.
RESULTS: During the observation period, 65,675 cases of acute appendicitis occurred in Ontario. Of these, 58% of the patients were male and 35.5% had perforation. The mean (and standard deviation [SD]) LOS for patients with perforation was 6.2 (5.3) days versus 3 (1.8) days for patients with no perforation (p < 0.001). The age-specific incidence of acute appendicitis followed a similar pattern for males and females, but males had higher rates in all age groups. The incidence was highest in those aged 10-19 years. The annual age and sex-adjusted incidence of acute appendicitis was 75 per 100,000 population. The female:male age-adjusted rate ratio was 1:1.4. During the study period, the rate of acute appendicitis decreased by 5.1%, but the rate of appendicitis with perforation increased by 13%. A significant seasonal effect was also observed, with the rate of acute appendicitis being higher in the summer months.
CONCLUSIONS: Appendicitis is more common in males, in those aged 10-19 years, and during the summer months. The frequency of acute appendicitis appears to be decreasing whereas the proportion of cases with perforation appears to be increasing. This may reflect a change in the population structure in Ontario and restrictions placed on the patient access to the health care system.