Diagnostic value of ultrasound compared to CT in patients with suspected acute appendicitis

Objective: The aim of this study was to evaluate the diagnostic efficacy of ultrasound compared to CT in patients with suspected acute appendicitis, thereby reducing unnecessary CT examinations and associated radiation exposure. Methods: A total of 108 patients who underwent ultrasound and/or CT examinations for suspected acute appendicitis were enrolled in this study from February 2014 to August 2015 at our hospital. The ultrasound, CT and pathological records were retrospectively analyzed to evaluate the diagnostic efficacy of the two imaging modalities on acute appendicitis. Results: The sensitivity, specificity, positive predictive value, negative predictive value and accuracy on the diagnosis of acute appendicitis was 85.5%, 66.7%, 98.5%, 15.4% and 84.8% with ultrasound and 87.8%, 75.0%, 97.7%, 33.3% and 86.8% with CT, respectively. Among these patients, there were 24 cases imaged with both modalities, the analysis showed that AUC of ultrasound was larger than that of CT, while the difference was not statistically significant. For thickened appendix, the display rate of ultrasound was 63.5%, which was significantly higher than that of CT (31.9%) (P=0.001). For enlarged appendix, the display rates of ultrasound and CT were similar (82.4% and 93.6%, respectively). Additionally, for different pathological types of appendicitis, the detective rates for ultrasound and CT were as follows: 81.8% and 60.0% for acute simple appendicitis, 86.0% and 92.6% for acute purulent appendicitis, 90.9% and 100% for acute gangrenous appendicitis, while no significant difference was found between the two imaging modalities. Conclusion: Ultrasound should be used as the first-line imaging modality for diagnosing acute appendicitis, and complementary CT may be performed if inconclusive acute appendicitis is indicated.