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

Abstract

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.

MR Imaging-based Evaluation of Mesenteric Ischemia Caused by Strangulated Small Bowel Obstruction and Mesenteric Venous Occlusion: An Experimental Study Using Rabbits

“…Single-shot T 2 WI sequences such as HASTE are widely used to assess patients with acute abdominal pain because these sequences can obtain images in the lower abdominal region for approximately 20 s with few motion artifacts due to vascular pulsation, respiratory motion, and bowel peristalsis because single-shot T 2 WI with one radiofrequency excitation pulse generates a long train of spin echoes. 9,12 However, its spatial resolution is lower than that of turbo spin echo T 2 WI because of blurring, especially in small structures possessing a short T 2 relaxation time. [31][32][33] Therefore, single-shot T 2 WI is appropriate for evaluating anatomical structures, but it is not suitable for assessing subtle changes of signal intensity.…”

“…6 Consequently, MRI is recommended for acute abdominal pain in pregnant patients. 7,8 The use of MRI in patients with acute abdominal pain was previously limited to patients with biliary and gynecological disease that could not be diagnosed using CT; however, several studies reported that MRI is helpful for diagnosing acute abdominal pain caused by not only acute appendicitis [9][10][11][12] but also other diseases. [13][14][15] MRI has potentially high-contrast resolution, and it can illuminate ischemic changes caused by acute mesenteric ischemia.…”

Usefulness of CT Scan in Diagnosing Acute Appendicitis in Patients with Low Alvarado Scores

“…16 Although various studies have documented validity of CT against higher AS, 17 however, only a few have emphasized upon its prime utility in patients with low AS or equivocal cases that may end up in having aetiologies other than acute appendicitis. 18 Prompt identification of an alternate diagnosis in such patients is strategic not only to reduce patient anxiety and hospital stay but also to guide clinicians towards specific treatment and avoid negative surgery (appendectomy). Therefore, we aim to highlight usefulness of CT imaging in such stratum of patients (i.e., with clinical suspicion of acute appendicitis and equivocal AS).…”

Acute Appendicitis and Negative or Inconclusive Results at Initial US in Adult, Pediatric, and Pregnant Patients: What to Do Next?

“…The meta-analysis by Eng et al (10) included 37 studies and evaluated a relevant number of patients: 717 patients with US examinations, 2525 patients with CT examinations, and 714 patients with MRI. The authors concluded that second-line US, CT, and MRI have comparable and high accuracy in helping to diagnose appendicitis in children, adults, and pregnant women after an initial US examination with negative or inconclusive results.…”

“…The value of a meta-analysis depends on the methodologic process, quality of the included studies, and of the assessment of the studies' heterogeneity. Eng et al (10) followed rigorous methods for study analysis and inclusion criteria on the basis of the recommendations from the Preferred Reporting Items for Systematic Reviews and Meta-analyses. The authors included only studies that focused on the evaluation of diagnostic accuracy of a second-line US, CT, or MRI after an initial US.…”