The Confounding Ultrasound Diagnosis of Ectopic Pregnancy: Lessons From Peer Learning

As the treatment of ectopic pregnancy (EP) has shifted increasingly to medical therapies, the ultrasound (US) diagnosis of EP must necessarily favor specificity over sensitivity. Our review of peer learning cases of EP and early intrauterine pregnancies found several types of pitfalls and problems, which will be described in this essay. These issues include the following: differentiation of tubal EP from a corpus luteum by echogenicity relative to ovarian parenchyma, push technique, and claw sign; how to distinguish interstitial EP from eccentrically located intrauterine pregnancies (angular); use of trophoblastic flow in abnormal intrauterine locations to help identify cesarean scar or cervical implantations; recognition that hemoperitoneum without visualized EP may be due to EP or hemorrhagic cyst; and that distinguishing an abortion in progress from a pregnancy of unknown location may not always be possible and requires clinical follow-up. This essay will also illustrate the consensus terminology that our radiology department has developed in conjunction with our obstetrics and gynecology colleagues to communicate clear diagnoses and reduce the risk of misdiagnosis and adverse outcomes.