Rationale and Objectives: To assess the necessity of intravenous contrast medium for abdominopelvic computed tomography (CT) diagnosis of acute appendicitis (APP) among adult patients with right lower quadrant (RLQ) abdominal pain at emergency department (ED). Materials and Methods: ED patients with clinical suspicion of APP from RLQ pain for a period of 8 months were enrolled retrospectively. Both pre- and postintravenous contrast-enhanced CT scans were performed for these patients. The visibility of vermiform appendix and specific CT findings of APP were recorded separately for noncontrast CT (NCT) and contrast-enhanced CT (CCT) images without knowledge of the patient's identity and final diagnosis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CT diagnosis for APP were compared between the two groups. The ease of identifying appendix was also compared. Results: Forty-two (42.0%) of the 100 patients (55 males, 45 females; age range, 16-90 years; mean age, 49.3 years) were APP. There was no significant difference for the visibility of appendix (94% vs. 91%; P = .589) and radiological characters between the CCT and NCT groups. There were significant differences between the two groups for sensitivity (100% vs. 90.5%; P = .036), specificity (94.8% vs. 100%; P = .038), PPV (93.3% vs. 100%; P = .021), NPV (100% vs. 93.5%; P = .021), but no significant difference for accuracy (97% vs. 96%; P = 1). The appendix was easier to detect on CCT than NCT images (P = .013). Conclusion: The diagnostic sensitivity of CCT was significantly better than that of NCT. Intravenous contrast administration could also make doctors easier in indentifying appendixes.
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