• James T Rhea, Elkan F Halpern, Thomas Ptak, James N Lawrason, Richard Sacknoff, and Robert A Novelline.
• Harvard Medical School and Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, USA. jrhea@sfghrad.uscsf.edu
• AJR Am J Roentgenol. 2005 Jun 1; 184 (6): 1802-8.

ObjectiveAppendiceal CT was introduced at our hospital in 1996 and now is used in most patients. The use of appendiceal CT has generated controversy and mixed results in various investigations. Our purpose was to determine the percentage of patients for whom CT was performed, incidence of appendicitis, accuracy of CT, percentage of equivocal interpretations, and negative appendectomy rates for those patients who did and did not undergo CT.Materials And MethodsPatient records from 2001 that included clinical or CT preoperative examination were analyzed, with follow-up through 2003. Patient age and sex, clinical presentation, CT techniques, CT interpretations, operative reports, pathology reports, and patient disposition were determined. Final diagnoses were provided by pathologic criteria, patient follow-up, or patient survey. Statistical analysis included Fisher's exact test and receiver operating characteristic (ROC) curves.ResultsOf 753 patients, 663 (88%) were examined on CT for suspected appendicitis and 90 had an appendectomy without undergoing CT. The incidence of appendicitis in the patients who underwent CT was 39.2%. The sensitivity and specificity of CT were 99% and 95%, respectively; the area under the ROC curve was 0.9896; and the percentage of equivocal CT interpretations was 3.3%. The false-negative appendectomy rates were 3.0% and 5.6% for patients with and without CT, respectively (for all patients, p = 0.326; for female pediatric patients, p = 0.030).ConclusionFive years ago, the negative appendectomy rate dropped from 20% to 7%, and it is now 3.0%. The incidence of appendicitis in patients who are examined on CT is stable compared with similar cohorts from prior investigations. Patients who do not undergo CT also have a low negative appendectomy rate, but this relatively small group is selected on the basis of a convincing clinical presentation. Female pediatric patients likely would have a lower negative appendectomy rate with greater use of CT.

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