Mai Thieme MD, Presenter: Nothing to Disclose

Jaap Stoker MD, PhD, Abstract Co-Author: Research support, Koninklijke Philips Electronics NV

Bart M. Wiarda MD, Abstract Co-Author: Research grant, Siemens AG, Haque, Netherlands Research grant, Bayer AG, Berlin, Germany

The primary goal was to study the accuracy of Magnetic Resonance Imaging (MRI) as an alternative to Computed Tomography (CT) in patients suspected of acute appendicitis (AA) with a non-diagnostic ultrasonography (US). Secondly, to determine the accuracy of Diffusion Weighted Imaging (DWI) in diagnosing AA.

70 adult and pediatric patients (mean age 25, range 3-64) clinically suspected of AA and having a non-diagnostic US were included. All patients underwent abdominal MRI including DWI within 4hrs (mean 67min). Clinical and laboratory data as well as imaging findings were collected and analyzed. Follow-up included all available data for a period of at least 2 months.

AA was present in 29 patients (29/70, 41.4%). MRI was completed in all, in 3 no DWI was performed (technical problems (2); claustrophobia (1)). MRI was true positive in 28, false positive in 1, true negative in 40 and false negative in 1; sensitivity 96.6% and specificity 97.6%. The appendix was visualized in all but 4, the latter concerning 1 false negative and 3 patients with alternative diagnoses (terminal ileitis (2); mesenteric lymphadenitis (1)). DWI showed disturbed diffusion at the site of the inflamed appendix in all but one cases of AA. Twenty-seven of 29 patients with AA underwent DWI, demonstrating disturbed appendiceal diffusion in 26. In the non-AA group, 39 of 40 patients underwent DWI and in all there was normal appendiceal diffusion. Sensitivity of DWI is 96.3% and specificity is 100%.  

MRI has high sensitivity and specificity in diagnosing appendicitis in patients with inconclusive US. DWI showed disturbed diffusion in almost all patients with proven AA and has similar test accuracy as standard MRI sequences. Therefore DWI imaging has potential as single sequence MR protocol in AA. Further comparative studies with DWI are necessary.

MRI and DWI both have high accuracy in inconclusive US cases and might be considered as alternative to CT, obviating radiation exposure and the use of intravenous contrast medium.

Thieme, M, Stoker, J, Wiarda, B, Magnetic Resonance Imaging and Diffusion-weighted Imaging in Acute Appendicitis.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8003211.html