To determine if integrating magnetic resonance (MR) imaging into the workup of right lower quadrant pain in pregnant patients was associated with improved outcomes as measured by the negative laparotomy rate (NLR) and the perforation rate (PR).

Institutional review board approval was obtained for this retrospective review of medical records. Two hundred sixty-seven pregnant patients who underwent either surgery (n = 82) or an MR imaging examination (n = 217) because of suspicion of appendicitis between January 1, 1996, and August 31, 2011, were identified. Relevant ultrasonographic and MR imaging reports were classified as showing true-positive, false-positive, true-negative, false-negative, or equivocal findings. MR imaging utilization was analyzed to define pre– and post–MR imaging cohorts. NLR and PR were calculated for both cohorts and were compared by using a Fisher exact probability test. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for MR imaging were calculated.

MR imaging was introduced into the clinical workup in 2004. From 1996 to 2003, the NLR for pregnant patients was 55% (17 of 31), and the PR was 21% (three of 14). From 2004 to 2011, the NLR was 29% (15 of 51), and the PR was 26% (nine of 35). The 47% decline in the NLR ([55%–29%]/55%) was statistically significant (P = .02). The change in PR was not significant (P > .99). The sensitivity, specificity, PPV, and NPV of MR imaging in the diagnosis of appendicitis were 89% (17 of 19), 97% (187 of 193), 74% (17 of 23), and 99% (187 of 189), respectively.

The routine incorporation of MR imaging into the clinical workup for suspicion of appendicitis in pregnant patients at this institution was associated with a decrease in the NLR of 47% without a significant change in the PR.

© RSNA, 2013

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