Ultrasound of Interstitial Ectopic Pregnancy

In this radiology lecture, we review the ultrasound appearance of interstitial ectopic pregnancy!

Key teaching points include:

Interstitial ectopic pregnancies are rare, occurring in proximal (interstitial) portion of fallopian tube within muscle wall of uterus
Much less common than tubal ectopic pregnancy occurring in the more distal ampullary and isthmic portions of fallopian tube
Interstitial ectopic pregnancies are important because higher morbidity and mortality due to later presentation and risk of life-threatening hemorrhage
Abnormally eccentric gestational sac with thin surrounding myometrium: less than 5 mm myometrial thickness highly suspicious
“Interstitial line” sign: Thin echogenic line extending from endometrial cavity to ectopic gestational sac. Thought to represent interstitial portion of tube separating the ectopic pregnancy from the endometrium
Medical: Systemic MTX, may also be injected into gestational sac
Surgery: Cornual wedge resection when ruptured versus hysterectomy
Can be confused with angular pregnancy: Rare, intrauterine pregnancy with implantation eccentrically high at the lateral angle of uterine cavity. More medial than interstitial ectopic pregnancies. No interstitial line sign, and greater than 5 mm thickness of overlying myometrial mantle
Angular pregnancy can result in normal pregnancy, but increased risk of miscarriage and uterine rupture. Should be followed closely to ensure growth towards endometrial cavity
Angular pregnancy is sometimes referred to as a “cornual pregnancy,” but controversial as earliest use of term cornual pregnancy refers to intrauterine implantations in anomalous unicornuate, bicornuate or septate uteri. To avoid confusion, best to specifically describe whether the gestational sac is intrauterine or ectopic

To learn more about the Samsung RS85 Prestige ultrasound system, please visit: https://www.bostonimaging.com/rs85-prestige-ultrasound-system-4

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