Acute Appendicitis: A Meta-Analysis of the Diagnostic Accuracy of US, CT, and MRI as Second-Line Imaging Tests after an Initial US.

Purpose To evaluate the sensitivity, specificity, and diagnostic odds ratios of US, CT, and MRI as second-line imaging modalities after initial US for assessing acute appendicitis in children and adults. Materials and Methods A literature search was conducted in Medline and Embase to identify articles that used surgery or histopathologic examination alone or in combination with clinical follow-up or chart review to evaluate the diagnostic accuracy of second-line imaging modalities. The quality of articles was assessed by using the Quality Assessment of Diagnostic Accuracy Studies-2 and the Standards for Reporting of Diagnostic Accuracy tools. Results For studies of children, the number of studies and patients were as follows: US, six studies and 548 patients; CT, nine studies and 1498 patients; MRI, five studies and 287 patients. For studies of adults, the number of studies and patients were as follows: US, three studies and 169 patients; CT, 11 studies and 1027 patients; MRI, six studies and 427 patients. Pooled sensitivities and specificities of second-line US for diagnosis of appendicitis in children were 91.3% (95% confidence interval [CI]: 83.8%, 95.5%) and 95.2% (95% CI: 91.8%, 97.3%), respectively; and in adults, the pooled sensitivities and specificities were 83.1% (95% CI: 70.3%, 91.1%) and 90.9% (95% CI: 59.3%, 98.6%), respectively. Regarding second-line CT in children, the pooled sensitivities and specificities were 96.2% (95% CI: 93.2%, 97.8%) and 94.6% (95% CI: 92.8%, 95.9%); and in adults, the pooled sensitivities and specificities were 89.9% (95% CI: 85.4%, 93.2%) and 93.6% (95% CI: 91.2%, 95.3%), respectively. Regarding second-line MRI in children, pooled sensitivities and specificities were 97.4% (95% CI: 85.8%, 100%) and 97.1% (95% CI: 92.1%, 99.0%); and in adults, the pooled sensitivities and specificities were 89.9% (95% CI: 84.8%, 93.5%) and 93.6% (95% CI: 90.9%, 95.5%), respectively. Conclusion Second-line US, CT, and MRI have comparable and high accuracy in helping to diagnose appendicitis in children and adults, including pregnant women. All three modalities may be valid as second-line imaging in a clinical imaging pathway for diagnosis and management of appendicitis. © RSNA, 2018 Online supplemental material is available for this article.