ARRS 2022 Abstracts

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E1634. Imaging of Pregnancies in the Cornual Region and Review of Interstitial Ectopic Pregnancies
Authors
  1. David Mittelstein; Keck School of Medicine of the University of Southern California
  2. Daphne Walker; Keck School of Medicine of the University of Southern California
Background
Approximately 1–3% of ectopic pregnancies implant in the interstitial portion of the fallopian tube that is embedded within the uterine myometrium. These interstitial ectopic pregnancies pose greater risks for rupture and hemorrhage than other ectopic pregnancies due to location and anatomy, which allows the gestation to grow into the second trimester. If there is a misdiagnosis or delay in diagnosis, patients with interstitial ectopic pregnancies can present with catastrophic rupture. Interstitial ectopic pregnancy must be distinguished from viable eccentric pregnancies, including: 1) pregnancies in uteri with Mullerian malformations, and 2) angular pregnancy in the lateral angle of the uterine cavity. The risk of misdiagnoses has been credited for both the relatively high mortality rate of interstitial pregnancies of up to 2.5% and for the iatrogenic loss of desirable viable pregnancies. As such, it is important for radiologists to recognize diagnostic ultrasound features of the ectopic pregnancy, including its extra-uterine location and the diagnostic “interstitial line sign.” 3D ultrasound (US) and MRI imaging can be utilized in challenging cases with pregnancies in the cornual region including: Mullerian malformations, fibroid uteri, angular pregnancies, and interstitial ectopics.

Educational Goals / Teaching Points
This exhibit aims to 1) review anatomy of the uterotubal junction; 2) develop an approach to imaging pregnancies in the cornual region; 3) review interstitial ectopic pregnancies and spectrum of imaging findings; and 4) present challenging cases with imaging findings, management, and outcomes.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Four cases are presented in this exhibit. Case 1 is an eccentric right intrauterine pregnancy in arcuate uterus. Case 2 is an eccentric intrauterine pregnancy due to fibroid uterus. Case 3 is an interstitial ectopic pregnancy with interstitial line sign on 2D US. Case 4 is an interstitial ectopic pregnancy with interstitial line sign on 3D US.

Conclusion
Distinguishing an interstitial ectopic pregnancy from an eccentric intrauterine or angular pregnancy can sometimes be challenging. Generally, in practice the correct diagnosis for an eccentric pregnancy in the cornual region can and should be made using 2D transvaginal US imaging. For cases of eccentric pregnancies, including interstitial ectopics, which are not diagnostic on 2D US, additional imaging including 3D US or MRI should be obtained. The “interstitial line sign” is diagnostic for interstitial ectopics, and although this finding is not demonstrated in all cases of interstitial ectopic pregnancies, additional imaging with 2D cine imaging, 3D transvaginal US imaging, and MRI may demonstrate this sign. Given the morbidity and mortality risk of rupture from interstitial ectopic pregnancies, an early diagnosis is critical. Radiologists must know how to approach imaging pregnancies in the cornual region, the spectrum of US findings for interstitial ectopic pregnancies, and when to use adjunct imaging for accurate diagnoses.