E2170. That’s Eccentric: A Resident’s Guide to Differentiating Between Interstitial Ectopic and Angular Pregnancies
  1. Sean Wagner; University of North Carolina Hospitals
  2. Bhavana Pottabatula; University of North Carolina Hospitals
  3. Ellie Lee; University of North Carolina Hospitals
  4. Katrina McGinty; University of North Carolina Hospitals
  5. Lauren Burke; University of North Carolina Hospitals
  6. Kristen Olinger; University of North Carolina Hospitals
Implantation of an embryo outside of the normal intrauterine location, or ectopic pregnancy, is said to occur in approximately 2% of all pregnancies in the United States. The vast majority of these pregnancies occur within the fallopian tubes. Eccentric pregnancy refers to implantation of the gestational sac at the utero-tubal junction. Interstitial ectopic pregnancy, a subset within eccentric pregnancy, refers to implantation within the proximal/myometrial tubal segment. Although this type of implantation is not uncommonly encountered on first trimester obstetrical ultrasound, it can be difficult to distinguish from angular and/or cornual pregnancy, particularly for trainees and providers with limited experience. This exhibit aims to provide a useful review to aid in the important distinction between these entities.

Educational Goals / Teaching Points
It is of upmost importance to accurately distinguish an angular pregnancy, which is a technically viable, although high risk intrauterine pregnancy, from an interstitial ectopic pregnancy, which is associated with a higher risk of uterine rupture and hemorrhage compared to the traditional tubal ectopic pregnancies. This exhibit will review the detailed anatomy, incidence, and appearance by ultrasound and magnetic resonance imaging (MRI) of these entities. There will also be additional discussion of management and complications associated with each type of pregnancy.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Angular pregnancy (high eccentric positioning of the gestational sac in the fundus/cornua, located more medially compared to interstitial ectopic, viable, but high risk for maternal hemorrhage). Interstitial ectopic (implantation within the myometrial portion of the tube has ability to grow larger than traditional tubal ectopic, high risk of rupture, massive hemorrhage, and maternal mortality). Cornual pregnancy (essentially equivalent to angular pregnancy, but with an underlying uterine anomaly).

Although ectopic pregnancy only occurs in approximately 2% of all pregnancies, the emergent finding results in a disproportionate amount of maternal morbidity and mortality. It is vital for the interpreting radiologist to provide quick and accurate diagnosis to ensure optimal patient triage and care. Interstitial ectopic pregnancy can be a difficult diagnosis due to its similarities to other types of ectopic pregnancies. However, it is essential to differentiate this entity from other diagnoses, given its comparative high risk of rupture, hemorrhage, and patient mortality.