Objective -To clarify poorly understood epidemiological features of appendicitis.
Design -Retrospective study of consecutive cases from a defined population and analysis of data from published studies.
Setting -County of Jonkoping, Sweden. 3,029 patients who underwent operation in 1984-9 and 4,717 patients from the county town who underwent operation in 1970-89, all for suspected appendicitis, plus 48,426 cases from six reported studies.
Main outcome measures -Incidences specific for age and sex and temporal trends of perforating and non-perforating appendicitis and removal of a normal appendix. Associations between diagnostic accuracy, rate of perforation, and incidences of removal of a normal appendix and of perforating and non-perforating appendicitis.
Results -The incidence of appendicitis was 116/100,000 inhabitants. Appendicitis was more common in male patients. The incidence of perforating appendicitis was independent of age, stable over time, and uninfluenced by the rate of laparotomy, whereas the incidence of non-perforating appendicitis was age dependent, decreasing over time, and related to the diagnostic accuracy and rate of removal of a normal appendix.
Conclusions -Perforating and non-perforating appendicitis seem to be separate entities, and appendicitis that resolves spontaneously is common. This may have important implications for managing suspected appendicitis.