Right lower quadrant pain: Value of the nonvisualized appendix in patients at multidetector CT

Purpose: To retrospectively determine the value of the nonvisualized appendix at multidetector computed tomography (CT) in patients with acute right lower quadrant pain in whom appendicitis was a consideration. Materials and Methods: Institutional review board approval was obtained for this HIPAA-compliant study, with waiver of informed consent. Records were retrospectively reviewed in patients who presented to the emergency department between April 29 and October 31, 2003, with right lower quadrant pain. Scanning was performed with the same eight-detector row CT scanner by using oral and (unless contraindicated) intravenous contrast agents, and transverse and coronal reformations were obtained. Two radiologists prospectively evaluated all scans at the time of the examination and rendered a consensus opinion. Clinical follow-up of at least 3 months' duration was performed retrospectively for patients whose appendix was not visualized to determine whether appendicitis had developed. Statistical analysis and calculation of percentages with confidence intervals (CIs) were performed. Results: Of the 400 consecutive patients who underwent multidetector CT, 132 (33.0%) were male and 268 (67.0%) were female. Eighty patients (20.0%) had acute appendicitis and 79 (19.8%) had another cause for abdominal pain. A normal appendix with no other cause for pain was seen in 182 patients (45.5%). In 59 patients (14.8%), the appendix was not visualized. Of these 59 patients, 50 had adequate follow-up. Clinical follow-up was uneventful in 49 of these 50 patients. Thus, on otherwise normal multidetector CT scans in patients suspected of having acute appendicitis, nonvisualization of the appendix was negative for appendicitis in 98% (95% CI: 71%, 100%) of cases. Conversely, when the appendix was seen at multidetector CT and was abnormal, appendicitis was present in 95% (95% CI: 72%, 100%) of cases. Conclusion: In patients with right lower quadrant pain, a nonvisualized appendix at multidetector CT reliably excludes acute appendicitis.