Audit of Ultrasonography for Diagnosis of Acute Appendicitis: a Retrospective Study

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HS Fung, S Lau, JCW Siu, CM Chan, SCH Chan

Hong Kong J Radiol 2008;11:108-11

Objective: To determine the utility and accuracy of ultrasonography for the diagnosis of acute appendicitis.

Methods: In this retrospective study, 242 of 286 patients undergoing ultrasonography of the appendix from 1 June 2006 to 31 December 2006 were included. The ultrasonography report, pathology report, and clinical notes were reviewed. The pathology report was used as the gold standard for a diagnosis of acute appendicitis.

Results: The overall rate of visualisation of the appendix was 41.7%. Fifty six patients (23%) had a positive diagnosis of acute appendicitis by ultrasonography, 45 (19%) had a negative diagnosis, and 141 (58%) had an inconclusive diagnosis; 17 patients (7%) had an alternative diagnosis suggested by ultrasonography. Twenty nine patients (12%) underwent computed tomography on the basis of the ultrasonography report, 6 of whom had a positive diagnosis for acute appendicitis, 5 had a negative diagnosis, and 18 had an alternative diagnosis suggested by computed tomography. The sensitivity, specificity, positive predictive value, and negative predictive value of ultrasonography for acute appendicitis were 75.9%, 89.7%, 73.2%, and 91.0%, respectively, after adjusted calculation for the group with an inconclusive ultrasonography diagnosis.

Conclusions: The performance of ultrasonography for investigation of acute appendicitis at the Queen Elizabeth Hospital, Hong Kong, is comparable to the data reported in the literature. Ultrasonography is a useful and safe imaging modality for investigation of acute appendicitis, and computed tomography has a complementary role for the diagnosis of acute appendicitis and management of patients with right lower quadrant pain.