Misdiagnosis of Acute Appendicitis in the Emergency Department: Prevalence, Associated Factors, and Outcomes According to the Patients' Disposition

Background: Although abdominal pain is one of the most common complaints of patients presenting to the emergency department (ED), and acute appendicitis is a leading surgical differential diagnosis of patients presenting with abdominal pain, the diagnosis of acute appendicitis remains challenging. We examined the missed diagnosis rate of acute appendicitis in one ED and evaluated the association between disposition (discharge home or hospitalization in the wrong department) and complicated appendicitis. Methods: We retrospectively evaluated the medical records of patients with acute appendicitis and periappendicular abscess from January 1, 2013, to December 31, 2016. Results: The diagnosis of acute appendicitis was missed in 7.1% of patients (90/1,268) at their first ED encounter: 44 were discharged, and 47 were hospitalized with a wrong diagnosis (1 female patient was both discharged and then hospitalized with an incorrect diagnosis). Compared to the patients who were correctly diagnosed, patients with a missed diagnosis were older (median age 29 years vs 23 years, P=0.022), their time between ED first encounter and surgery was longer (median 29.5 hours vs 9.3 hours, P<0.001), and their rate of complicated appendicitis was higher (54.4% vs 27.5%, P<0.001). Missed females were more commonly hospitalized (26/39), while missed males were more commonly discharged from the ED (31/52) (P=0.019). No differences in the time between the first ED encounter and surgery (29.6 hours vs 29.6 hours, P=0.29) and the rate of complicated appendicitis (63.8% vs 43.2%, P=0.06) were noted between hospitalized patients with a wrong diagnosis and those discharged from the ED. Of the 25 patients with periappendicular abscesses, only 3 could be related to missed diagnoses during their first encounter in the ED. Conclusion: We found that 7.1% of patients were missed during their first encounter in the ED. Hospitalization in departments other than general surgery was not protective against delay in surgery or the development of complicated appendicitis. Periappendicular abscess was attributable to late referral rather than a missed diagnosis in most patients.