Suspected acute appendicitis:: Is ultrasonography or computed tomography the preferred imaging technique?

Objective: To compare the sensitivity and specificity of unenhanced spiral computed tomography (CT) and ultrasonography (US) in patients with suspected acute appendicitis. Design: Prospective study. Setting: University hospital, Germany. Subjects: 120 consecutive patients with acute appendicitis as a differential diagnosis, whose clinical findings were not enough to make operation essential, but were too severe to send home. Interventions: CT and US of the appendix. Main outcome measures: Sensitivity, specificity, and positive and negative predictive value. Results: The results were correlated with surgical and histopathological findings at appendicectomy or clinical follow-up. 93 patients had acute appendicitis, 27 patients did not. The sensitivity of CT was 95% and of US 87%. The corresponding specificities were 89% and 74%, positive predictive values 97% and 92%, negative predictive values 83% and 63%. In the 27 patients who did not have acute appendicitis, the correct diagnosis was established with CT in 14 patients and with US in eight. Conclusion: CT is more sensitive and specific than US in patients suspected of having acute appendicitis, but in whom the presentation is equivocal. The use of unenhanced spiral CT led to a significant improvement in the accuracy of preoperative diagnosis and a lower negative appendicectomy rate.