Epidemiology

Acute appendicitis is among the most common causes of lower abdominal pain leading patients to attend the accident and emergency department and the most common diagnosis made in young patients admitted to the hospital with an acute abdomen.[7] Around 50,000 cases of appendicitis were treated in hospitals in England in 2020 to 2021.[10]​​ Most cases occurred in the 20 to 59 year age group.[10] A large majority presented (46,297) as medical emergencies.[10]

One systematic review of population-based studies reported the pooled incidence of appendicitis or appendectomy in the US in the 21st century to be 100 per 100,000 person-years; the estimated number of cases in the US in 2015 was 378,614.[11]

In the US, the overall lifetime risk of developing acute appendicitis is 8% for males and 7% for females.[12] Data suggest a rapid increase in incidence in newly industrialised countries.[11]

Acute appendicitis most commonly occurs between the ages of 10 and 30 years, with the highest incidence in children and adolescence.[7][13]​ There is a slight male to female predominance (1.4:1).[2]

Risk factors

A balance of gastrointestinal microbial flora is important for prevention of infection, for digestion, and for providing important nutrients.[20] Frequent use of antibiotics and improved hygienic conditions lead to decreased exposure and/or imbalance of gastrointestinal microbial flora that may eventually lead to a modified response to viral infection and thereby trigger appendicitis.[21]

Children exposed to passive smoking have significantly increased incidence of acute appendicitis.[7][22]​ There is also an increased incidence of acute appendicitis in adult patients who smoke every day compared with adults who never smoked.[22][23]

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