Pregnancy in a rudimentary horn: multicenter’s MRI features of a rare condition

Purpose To describe the MRI features of rudimentary horn pregnancy (RHP) with surgical correlations. Methods Nine women with a RHP underwent preoperative pelvic MRI. MRI protocol included T2- ( n = 9), T1- ( n = 7), and fat-suppressed contrast-enhanced T1-weighted sequences ( n = 4). Two pelvic radiologists retrospectively analyzed MR images to assess the following MRI features: presence of a myometrium around the gestational sac (GS) and characteristics of its wall, GS surrounded by myometrium in contact with the round ligament, communication of the GS with the endometrial cavity of the main horn, continuity of the GS with the cervix, fibrous or muscular GS attachment to the main horn, lateral deviation, and endometrial thickness of the main horn. Ovaries and tubes were also assessed. MRI features were correlated with surgical findings. Results Seven of the nine women [29 ± 6 SD years (range 16–37 years)] underwent surgical management. The first US diagnosed RHP in only 1/9 patients. All pregnancies were diagnosed using MRI. RHP was all located in the rudimentary horn of a unicornuate uterus. All the GS was surrounded by myometrium in contact with the round ligament. None of the RHP displayed communication with the endometrial cavity of the main horn nor with the cervix. An attachment between the RHP and the main horn was seen in 3/9 patients. All the main horns were lateralized and empty. Conclusion MRI diagnosed RHP in all patients by identifying the GS surrounded by myometrium in contact with the round ligament and the absence of continuity between the GS and the cervix. Level of evidence IV—retrospective study. Graphical abstract