Value of Us in Patients with Equivocal CT Findings of Acute Appendicitis: Comparison with CT Reassessment

Abstract

To compare diagnostic values of ultrasound (US) and CT reassessment in patients with equivocal CT findings of acute appendicitis, including those with coexistent inflammatory lesion. Patients with equivocal CT findings of acute appendicitis (n=115), who underwent US, were included. Two abdominal radiologists reviewed CT scans independently. They analyzed four CT findings (appendiceal wall enhancement, appendiceal wall thickening, intraluminal air in appendix, and coexistent inflammation) and make a diagnosis of acute appendicitis. Patients were categorized into positive and negative appendicitis based on previous US reports. The diagnostic performance, interobserver agreement in CT findings interpretation, and appendicitis likelihood were calculated. The area under the receiver operator characteristic curve (AUC, 0.960), sensitivity (100%), and specificity (92.1%) of US was higher than those of CT reassessment (reviewer 1: 0.697, 51.9% and 87.5%; reviewer 2: 0.759, 66.7% and 85.2%, respectively). In the coexistent inflammation group, the AUC (0.990), sensitivity (100%), and specificity (98.0%) of US were higher than those of CT reassessment (reviewer 1: 0.607, 27.3% and 94.1%, reviewer 2: 0.561, 14.3% and 98.0%%, respectively). Interobserver agreement in the CT diagnosis of appendicitis was moderate (κ=0.44). In patients with equivocal CT findings of acute appendicitis, US shows better diagnostic performance compared to CT reassessment, and helps differentiate between acute appendicitis and periappendicitis.