MRI of acute appendicitis in pregnancy: navigating diagnostic pitfalls and challenges

Non-contrast magnetic resonance imaging (MRI) is the preferred cross-sectional imaging modality for suspected appendicitis in pregnancy, yet its interpretation is uniquely challenging. This pictorial review moves beyond simple appendiceal diameter thresholds to the practical pitfalls encountered in daily practice. We show how the enlarging gravid uterus displaces the appendix and how physiologic changes mask inflammatory signs. We also address the diagnostic uncertainty of the equivocal appendix and the need to recognize subtle secondary features on MRI. We then detail several important entities that may confound interpretation, either by mimicking an inflamed appendix or by obscuring a normal one: pelvic venous engorgement, terminal ileitis, cecal diverticulitis, ovarian torsion, and ectopic pregnancy. For each, we highlight the features that help distinguish them. Finally, we discuss technical limitations such as field inhomogeneity and motion artifacts. We present a stepwise approach to locating the appendix paired with a problem-solving strategy that combines non-fat-suppressed and fat-suppressed T2-weighted sequences. By recognizing these multifaceted pearls and pitfalls, radiologists can improve diagnostic confidence and optimize care in this challenging population.