Normal MRI abdomen in pregnancy
Citation, DOI & case data
21/40 pregnant. Lower abdominal pain. US showed right hydronephrosis but no other abnormalities.
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Intrauterine pregnancy confirmed but not interrogated in detail. The appendix is not clearly identified. However, there are no signs of acute appendicitis with no edema or free fluid near the cecal pole, and no focus of abnormal restriction diffusion. Incidental note is made of right-sided physiologic hydronephrosis caused by compression of the ureter between the uterus and the right psoas muscle, and distension of the right ovarian vein.
The appendix may not be clearly identified on MRI in pregnancy for a number of reasons, including the limited spatial resolution compared to CT, and the alteration in anatomy caused by the gravid uterus. The absence of ancillary signs of acute appendicitis, such as edema and fluid in the region of the cecal pole on fat-saturated images and the lack of restriction of diffusion are helpful in confirming that there is no acute appendicitis. The pregnancy progressed to term with no requirement for surgical intervention.
This study also demonstrated two tubular structures in the right retroperitoneum that may be mistaken for each other, or for the appendix; the engorged right ovarian vein and the distended right ureter. The ureter is seen as a high signal structure on both the SSFSE and gradient echo sequences, whereas the ovarian vein is usually low signal on SSFSE (due to flow void) and high signal on gradient echo; these signal changes may be altered in the presence of ovarian vein thrombosis.