Objective: To measure and describe changes in the incidence of appendicectomy in the population of Western Australia (WA) for 1981-1997.
Design: Population-based incidence study using hospital discharge data.
Setting: All hospitals in WA (1981-1997).
Patients: All patients who underwent an appendicectomy in WA hospitals.
Main outcome measures: Changes in the incidence of appendicectomy procedures over time; age-standardised rates and age-sex profiles of four appendicectomy subgroups: (1) acute emergency admission, (2) other emergency admission, (3) incidental appendicectomy and (4) other appendicectomy.
Results: From 1981 to 1997, there were 59,749 appendicectomies in WA hospitals. The age-standardised rate of appendicectomy declined by 63% in metropolitan females, by 44% in non-metropolitan females, by 41% in metropolitan males and by 21% in non-metropolitan males. The rate of decline was significantly greater in females and in metropolitan patients. From 1988 to 1997, acute emergency admission for appendicectomy was the most common admission status and was more common in males than females (122 v 103 per 100,000 person-years) and in non-metropolitan areas. The rate of incidental appendicectomy was higher among females than males (20 v 7 per 100,000 person-years). From 1988 to 1997, recorded diagnosis coding for appendicitis became more specific, with a marked reduction in the use of the "unspecified" appendicitis code.
Conclusions: The overall incidence of appendicectomy has declined markedly in WA and includes a decline in the practice of incidental appendicectomy. The trend was greatest in the metropolitan hospitals.