MRI: first-line imaging modality for pregnant patients with suspected appendicitis.

Purpose: The purpose of our study was to evaluate the sensitivity, specificity, and accuracy of ultrasound (US) as compared to magnetic resonance imaging (MRI) in pregnant patients with suspected appendicitis for visualization of the appendix, accuracy at diagnosing acute appendicitis, the ability of each modality to identify alternate diagnoses of pain and whether gestational age (GA) has an association with appendix identification rates.

Methods: We retrospectively reviewed the records of 140 pregnant patients with suspected appendicitis to determine the efficacy of US and MRI to identify the appendix, diagnose or exclude acute appendicitis, identify alternative etiologies for clinical presentation, and the affect of GA on identification of the appendix. Imaging results were correlated with surgical pathology in patients who underwent surgery. The electronic medical record was used to assess clinical outcomes in patients who did not undergo surgery.

Results: The appendix was visualized in 7% (8/117) of US exams and in 80% (91/114) of MRI exams. Alternate etiologies of pathology were determined in 3% (3/117) of US exams and 12% (14/114) of MRI exams. The sensitivity and specificity of MRI for acute appendicitis were both 100% and 98%, respectively, as compared to 18% and 99%, respectively, with US. GA did not affect MRI or ultrasound visualization rates of the appendix.

Conclusion: Given the low likelihood of visualization of the appendix at US, the excellent accuracy of MRI and the ability of MRI to identify alternate diagnoses, we suggest that at certain institutions MRI may be considered a first-line imaging modality for pregnant patients of any GA with suspected appendicitis.