The Potential Role of Ultrasound in the Work-up of Appendicitis in the Emergency Department.

BACKGROUND: Acute appendicitis is common in the adult emergency department (ED). Computed tomography (CT) scan is frequently used to diagnose this condition, but ultrasound (US)-commonly used in pediatric diagnosis-may also have a role.

OBJECTIVES: Review the clinical utility and define the frequency and diagnostic accuracy of US to diagnose appendicitis in an adult population in the ED setting.

METHODS: Retrospective cohort study of patients who underwent appendiceal US in an academic, tertiary ED from July 2013-October 2015.

RESULTS: There were 174 patients included, of which 39 (22%) had pathology-confirmed appendicitis. There were 25 patients who had an US scan that was positive for appendicitis, 146 (84%) were indeterminate, and 3 (1.7%) were negative. Among patients with a positive US, 25/25 (100%, 95% confidence interval [CI] 84-100%) had appendicitis, 32/146 (22%, 95% CI 16-29%) with an indeterminate US had appendicitis, and 0/3 (0%, 95% CI 0-6.2%) with a negative US had appendicitis. In the 28 definitive cases, US had a sensitivity of 64%, specificity of 2%, positive predictive value of 100%, and negative predictive value of 100%. The likelihood ratio positive and negative were 173 and 0, respectively.

CONCLUSION: Our initial data suggest that an US that shows appendicitis seems to be reliable; however, a high prevalence of indeterminate studies limits the diagnostic utility as a universal approach in adult patients in the ED setting. Larger studies are needed to identify which patient populations would benefit from US as the initial imaging modality, what factors contribute to the large numbers of indeterminate results, and if any interventions may reduce the number of indeterminate results.