Unenhanced MRI a high performer in detection of acute appendicitis

Even without contrast, MRI can provide highly accurate assessment of appendicitis-suspected abdominal pain. As a bonus, the modality offers a viable, radiation-free option for guiding evaluation of other-than-appendicitis discomfort in that same section of the stomach area, according to a 403-patient study published ahead of print in Radiology.

Led by Iva Petkovska, MD, study authors at the University of Arizona report that their retrospective data showed unenhanced MRI, when verified or refuted by surgical results and clinical follow-up, scoring impressively close to perfect.  

Specifically, of the 403 patients presenting in the ED with pain in the right lower quadrant of the abdomen, 67 had MR imaging findings that were positive for acute appendicitis, while 336 had negative findings and were offered alternate diagnoses.

Unenhanced MRI had a sensitivity of 97 percent (65 of the 67) and a specificity of 99.4 percent (334 of the 336).

The imaging was quite quick, too, with a mean total room time of 14 minutes (range, 8 to 62 minutes).

The authors note that all MR images were acquired on 1.5-T or 3-T scanners, and that exams were performed without breath holding and with neither oral nor intravenous contrast agents.

Study limitations include the authors’ inability to contact each patient who had negative MRI findings, as well as attending radiologists’ rarely classifying study results as indeterminate.

The latter result, they state, may owe to their practice protocol’s not calling for positive identification of the appendix when there are no inflammatory changes in the right lower quadrant.

“MR imaging without oral and intravenous contrast material may be used with high accuracy as a first-line imaging test in patients younger than 50 years who present to the ED and are suspected of having acute appendicitis,” Petkovska et al. conclude. “MR imaging also has the capability to be used to assess secondary causes of abdominal pain and is a viable imaging option to reduce exposure to ionizing radiation.”

Current ACR appropriateness criteria hold that CT is the preferred imaging modality for evaluating suspected acute appendicitis and other sources of pain in the right lower quadrant.