Magnetic Resonance Imaging for Acute Appendicitis in Pregnancy: Can Clinical Scores Predict when Imaging is Needed?

Purpose: Advanced imaging may augment the diagnostic milieux for presumed acute appendicitis (AA) during pregnancy, however it is not clear when such imaging modalities are indicated. The aim of this study was to assess the sensitivity and specificity of clinical scoring systems with the findings on magnetic resonance imaging (MRI) of AA in pregnant patients.

Methods: A retrospective cohort study between 2019 and 2021 was performed in two tertiary level centers. Pregnant patients presenting with suspected AA and non-diagnostic trans-abdominal ultrasound who underwent MRI as part of their evaluation were identified. Patient demographics, parity, gestation, presenting signs, and symptoms were documented. The Alvarado and Appendicitis Inflammatory Response (AIR) score for each patient were calculated and correlated with clinical and MRI findings. Univariate analysis was used to identify factors associated with AA on MRI.

Results: Of the 255 pregnant patients who underwent MRI, 33 (13%) had findings of AA. On univariate analysis, presentation during the second/third trimester, migration of pain, vomiting and RLQ tenderness correlated with MRI findings of AA. Whilst 5/77 (6.5%) of patients with an Alvarado score ≤4 had signs of AA on MRI, a score of ≥5 had a sensitivity, specificity, negative and positive predictive value of 84.8%, 36.6%, 94.0% and 17.2%. For an AIR score ≥ 5, this was 78.8%, 41.5%, 93.0%, and 16.7%, respectively.

Conclusions: Whilst clinical scoring systems may be useful in identifying which pregnant patients require MRI to be performed when AA is suspected, the low sensitivity implies further research is needed to refine the use of this valuable resource.