Does computed tomography have any additional value after sonography in patients with suspected acute appendicitis?

Objectives: The purpose of this study was to evaluate the additional value of supplementary computed tomography (CT) after sonography for diagnosing acute appendicitis.

Methods: Among 140 consecutive patients with suspected acute appendicitis who underwent both initial sonography and supplementary CT within 12 hours, 88 patients whose appendices could not be visualized on sonography were excluded. The remaining 52 patients (mean age, 37.3 years; range, 15-98 years) were enrolled in this study. Two radiologists retrospectively reviewed the findings of 52 sonographic and CT examinations, and the appendix of each patient was classified as normal, equivocal appendicitis, nonperforated acute appendicitis, or perforated appendicitis. Causes of right lower quadrant pain other than appendicitis were also recorded. The additional value of supplementary CT was evaluated by performing head-to-head comparisons between CT and sonographic results.

Results: No patients with a normal appendix on sonography showed appendicitis on CT. In addition, there were no patients with a sonographic diagnosis of appendicitis who had a normal appendix on CT. Ten patients (19.2%) were determined to have additional value gained from CT. Among these 10 patients, however, the additional information from CT affected treatment modality decisions in only 5.

Conclusions: Initial sonography can be as effective as CT in patients with suspected acute appendicitis when the results are definite. Supplementary CT should only be performed when sonography is inconclusive.