Can the Presence of a Surrounding Endometrium Differentiate Eccentrically Located Intrauterine Pregnancy from Interstitial Ectopic Pregnancy?

Abstract

Differentiation of an eccentric intrauterine pregnancy (IUP) from an interstitial ectopic pregnancy (EP) is challenging. No sign for differentiation is reported. The purpose of this study was to determine whether the presence of surrounding endometrium (SE) can distinguish eccentric IUP from interstitial EP. This study was approved by the institutional ethics board; consent acquisition was waived. Cases were identified using ultrasound (US) reports that included the words "interstitial," "cornual," and "angular." Blinded to official reports, one reviewer reviewed US examinations retrospectively for the presence of SE, defined as the extension of endometrial lining around the gestational sac (GS) as an indication of an eccentric IUP. US examinations without SE on the retrospective review were diagnosed as interstitial EP. Forty-four cases were identified from 2007 to 2015. On retrospective review, 20 cases were labeled as eccentric IUP and 24 as interstitial EP. Ten of the 20 cases retrospectively labeled as eccentric IUP had been reported and managed as eccentric IUP prospectively: four followed to a viable second trimester, and six had spontaneous abortion/termination. The remaining 10 cases retrospectively labeled eccentric IUPs because of the presence of SE had been reported and managed as interstitial EP on the official prospective report. There was follow-up suggestion of eccentric IUP in six of the latter discordant pregnancies with non-concordant retrospective and prospective diagnosis: three had hysteroscopy/curettage demonstrating retained products, two had US follow-up showing the GS moving farther down in the uterine cavity, and in one patient, the GS was shown to pass per vagina. Twenty-four of the 44 cases were called interstitial EP both on the retrospective and prospective reviews and were managed as interstitial EP. Noneof these patients (without SE) had follow-up suggestive of eccentric IUP. Our results suggest that the presence of surrounding endometrium around the GS allows for differentiation of eccentric IUP from interstitial EP.