Marjolein Leeuwenburgh MD, Presenter: Nothing to Disclose

Wouter Van Es MD, PhD, Abstract Co-Author: Nothing to Disclose

Jan-Willem C. Gratama MD, PhD, Abstract Co-Author: Nothing to Disclose

Patrick M. M. Bossuyt PhD, Abstract Co-Author: Nothing to Disclose

Marja A. Boermeester MD, PhD, Abstract Co-Author: Nothing to Disclose

Jaap Stoker MD, PhD, Abstract Co-Author: Nothing to Disclose

To identify the optimal imaging strategy in adult patients with suspected appendicitis.

We included consecutive patients with suspected appendicitis in one academic hospital and five large teaching hospitals. Patients underwent a standard practice protocol: initial US, followed by CT in case of negative or inconclusive US results. Additionally, all patients underwent MRI (HASTE, HASTE SPAIR, DWI), with the MRI reader blinded for the results of the other imaging methods. A final diagnosis was assigned by an expert panel based on histopathology and clinical follow up after 3 months. We evaluated the sensitivity and specificity of the following scenarios: (1) US only;(2) US in all patients followed by CT after a negative or inconclusive US;(3) US followed by MRI after a negative or inconclusive US;(4) MRI only. Statistical differences between strategies were evaluated with the McNemar test.

We performed 229 US, 126 CT and 223 MRI examinations in 230 patients (mean age 38 years, 41% male). The expert panel assigned acute appendicitis as final diagnosis in 118 patients (51%). Sensitivity of US only was 0.76 (95%CI 0.68-0.83); specificity 0.94 (95% CI 0.88-0.97). Conditional imaging strategies with CT or MR after a negative or inconclusive US resulted in an significantly increased sensitivity (p < 0.001) of 0.97 (95%CI 0.93-0.99) and 0.99 (95%CI 0.95-1.00) and a specificity of 0.91 (95%CI 0.84-0.95) and 0.88 (95%CI 0.81-0.93) respectively. Conditional strategies with CT and MRI had comparable results for sensitivity and specificity (p = 0.500 and p = 0.453). The MRI only strategy had a high sensitivity (0.97, 95% CI 0.92-0.99) and specificity (0.93, 95%CI 0.87-0.97). 

Using US only would miss too many patients with acute appendicitis. Additional CT or MRI after a negative or inconclusive US have comparable accuracy and improve results. The choice for either technique can be based on the risk of ionizing radiation exposure, contrast nephropathy and allergy, on costs and experience. An MRI only strategy could be an alternative approach.

MRI is an appropriate replacement for CT in detecting acute appendicitis in adult patients in the emergency department, without the risks associated with ionizing radiation and contrast agents.

Leeuwenburgh, M, Van Es, W, Gratama, J, Bossuyt, P, Boermeester, M, Stoker, J, Optimal Strategy in Patients with Suspected Acute Appendicitis: Can MRI Replace CT?.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011534.html