Gary Lee Brahm BMedSc,MD, Presenter: Nothing to Disclose

Ian Greg Ross MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to assess the significance of nonvisualization of the appendix on graded compression ultrasound when evaluating for acute appendicitis in the adult population, and the additional value of secondary signs of appendicitis.

Following institutional review board approval, the records of patients presenting to the emergency department between December 2007 and February 2010 with symptoms of acute appendicitis were retrospectively reviewed. Of these individuals, 116 patients underwent a Computed Tomography (CT) scan following nonvisualization of the appendix on ultrasound to further assess for acute appendicitis. Ultrasound images were reviewed by an experienced abdominal radiologist, with focused attention to the presence or absence of secondary signs of appendicitis such as echogenic fat, free fluid, or local lymphadenopathy. Comparison was then made with the formal report from the subsequent CT exam and histopathology reports when available. Statistical analysis, with calculation of sensitivity, specificity, and negative predictive value was performed.

In patients in whom the appendix was not directly visualized during the evaluation for acute appendicitis on ultrasound, the CT scan demonstrated an incidence of acute appendicitis of 16% with a negative prective value (NPV) of 84%. The absence of secondary signs of appendicitis in addition to nonvisualization of the appendix had a sensitivity of 79%, specificity of 85%, and negative predictive value of 95% for the diagnosis of appendicitis. This is an ongoing study and updated results will be provided at the time of presentation.

In the absence of direct visualization of the appendix without secondary signs of appendicitis on graded compression ultrasound, there is a low incidence of appendicitis. Further evaluation with CT examination should be reserved for those cases in which an alternate diagnosis is considered.

In cases in which the appendix is not visualized on ultrasound examination and no secondary signs of appendicitis are present, the incidence of acute appendicitis is very low.

Brahm, G, Ross, I, The Nonvisualized Appendix on Ultrasound: What Does It Mean?.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11006632.html