Michael J. Lane, MD ; David M. Liu, MD ; Mylinh D. Huynh, MD ; R. Brooke Jeffrey, Jr, MD ; Robert E. Mindelzun, MD ; Douglas S. Katz, MD

¹ From the Department of Radiology, Brooke Army Medical Center, 3851 Roger Brooke Dr, Ft Sam Houston, TX 78234-6200 (M.J.L.); the Department of Radiology, Stanford University, Calif (D.M.L., M.D.H., R.B.J., R.E.M.); the Department of Radiology, University of British Columbia, Victoria, Canada (D.M.L.); and the Department of Radiology, Winthrop University Hospital, Mineola, NY (D.S.K.). From the 1998 RSNA scientific assembly. Received September 24, 1998; revision requested October 26; final revision received March 11, 1999; revision accepted June 9.

PURPOSE: To determine the accuracy of helical computed tomography (CT) without the oral, intravenous, or rectal administration of contrast material in confirming suspected acute appendicitis.

MATERIALS AND METHODS: Three hundred consecutive patients referred from the departments of surgery and emergency medicine were examined for suspected acute appendicitis by using thin-section nonenhanced helical CT. All transverse CT scans were obtained in a single breath hold from the upper abdomen (T12 vertebra) to the pubic symphysis with 5-mm collimation and a pitch of 1.6. All scans were obtained without oral, intravenous, or rectal contrast material. Criteria for diagnosis of acute appendicitis included an enlarged appendix (>6 mm) and periappendiceal inflammation. CT diagnoses were recorded prospectively. Final diagnoses were established with the results of surgical or clinical follow-up or both.

RESULTS: There were 110 true-positive diagnoses, 181 true-negative diagnoses (63 of which were an alternative diagnosis correctly established prospectively), five false-negative diagnoses, and four false-positive diagnoses, which yielded a sensitivity of 96%, a specificity of 99%, and an accuracy of 97%.

CONCLUSION: Nonenhanced helical CT is a highly accurate technique for diagnosing or excluding acute appendicitis. Developing experience with the technique and understanding the subtleties of interpretation can further improve diagnostic accuracy.