Diagnostic Performance of Multidetector Computed Tomography for Suspected Acute Appendicitis

Background: Use of preoperative computed tomography for suspected acute appendicitis has dramatically increased since the introduction of multidetector CT (MDCT) scanners. Objective: To evaluate the diagnostic performance of MDCT for suspected acute appendicitis in adults. Design: Analysis of MDCT findings and clinical outcomes of consecutive adults referred for MDCT for suspected appendicitis from January 2000 to December 2009. Setting: Single academic medical center in the United States. Patients: 2871 adults. Measurements: Interpretation of nonfocused abdominopelvic MDCT scans by radiologists who were aware of the study indication. Posttest assessment of diagnostic performance of MDCT for acute appendicitis, according to the reference standard of final combined clinical, surgical, and pathology findings. Results: 675 of 2871 patients (23.5%) had confirmed acute appendicitis. The sensitivity, specificity, and negative and positive predictive values of MDCT were 98.5% (95% CI, 97.3% to 99.2%) (665 of 675 patients), 98.0% (CI, 97.4% to 98.6%) (2153 of 2196 patients), 99.5% (CI, 99.2% to 99.8%) (2153 of 2163 patients), and 93.9% (CI, 91.9% to 95.5%) (665 of 708 patients), respectively. Positive and negative likelihood ratios were 51.3 (CI, 38.1 to 69.0) and 0.015 (CI, 0.008 to 0.028), respectively. The overall rate of negative findings at appendectomy was 7.5% (CI, 5.8% to 9.7%) (54 of 716 patients), but would have decreased to 4.1% (28 of 690 patients) had surgery been avoided in 26 cases with true-negative findings on MDCT. The overall perforation rate was 17.8% (120 of 675 patients) but progressively decreased from 28.9% in 2000 to 11.5% in 2009. Multidetector computed tomography provided or suggested an alternative diagnosis in 893 of 2122 patients (42.1%) without appendicitis or appendectomy. Limitation: Possible referral bias, because some patients whose appendicitis was difficult to diagnose on clinical grounds may not have been referred for MDCT for evaluation of suspected appendicitis. Conclusion: Multidetector computed tomography is a useful test for routine evaluation of suspected appendicitis in adults.