Diagnostic performance and useful fndings of ultrasound re-evaluation for patients with equivocal CT features of acute appendicitis

Objective: To evaluate the diagnostic performance of ultrasound and to determine which ultrasound fndings are useful to differentiate appendicitis from nonappendicitis in patients who underwent ultrasound re-evaluation owing to equivocal CT features of acute appendicitis. Methods: 62 patients who underwent CT examinations for suspected appendicitis followed by ultrasound re-evaluation owing to equivocal CT fndings were included. Equivocal CT fndings were considered based on the presence of only one or two fndings among the CT criteria, and ultrasound re-evaluation was done based on a predefned structured report form. The diagnostic performance of ultrasound and independent variables to discriminate appendicitis from non-appendicitis were assessed. Results: There were 27 patients in the appendicitis group. The overall diagnostic performance of ultrasound re-evaluation was sensitivity of 96.3%, specifcity of 91.2% and accuracy of 91.9%. In terms of the performance of individual ultrasound fndings, probe-induced tenderness showed the highest accuracy (86.7%) with sensitivity of 74% and specifcity of 97%, followed by non-compressibility (accuracy 71.7%, sensitivity 85.2% and specifcity 60.6%). The independent ultrasound fndings for discriminating appendicitis were non-compressibility (p = 0.002) and increased flow on the appendiceal wall (p = 0.001). Conclusion: Ultrasound re-evaluation can be used to improve diagnostic accuracy in cases with equivocal CT features for diagnosing appendicitis. The presence of non-compressibility and increased vascular flow on the appendix wall are useful ultrasound fndings to discriminate appendicitis from nonappendicitis. Advances in knowledge: Ultrasound re-evaluation is useful to discriminate appendicitis from non-appendicitis when CT features are inconclusive.