Triaging of eccentric gestational sac in early pregnancy using two dimensional and three dimensional transvaginal ultrasound

Abstract

AbstractObjectives: Interstitial ectopic pregnancy and pregnancy in arudimentary horn of a unicornuate uterus are rare forms of ectopic pregnancy but carry a high risk for maternal morbidityand mortality. Their diagnosis is challenging and can be misdiagnosed with less dangerous conditions; namely: angular pregnancy or pregnancy in one side of septate or bicornuate uterus.This study aimed to differentiate between these four situationsto allow early detection that will enhance the prognosis.Methods: This is a retrospective study, carried out on 26 patients referred to a private referral center for obstetric and gynecology sonography, in the period from November 2019 tillNovember 2020. All cases were referred due to unusual eccenteric location of the gestational sac. In each case we assessed3 variables using 2D -TVUS which were: relation to the endometrium , interstitial line sign and condition of the overlyingmyometrium. We assessed also 2 variables using 3D- TVUSwhich were: shape of the uterine cavity and the relation of thegestational sac to the uterotubal junction.Results: It was found that the gestational sac (GS) is withinthe endometrium in angular pregnancy and pregnancy in septate and bicornuate uterus while GS is outside the endometrial interface in interstitial ectopic pregnancy and pregnancy inrudimentary horn of unicornuate uterus. The interstitial linesign was +ve and the overlying myometrium was thin only ininterstitial ectopic pregnancy. Cavity was normal in angularand interstitial ectopic pregnancy but it has a Mullerian fusionanomaly in cases of pregnancy in rudimentary horn of a unicornuate uterus and cases with pregnancy in one side of a septateor bicornuate uterus. GS was lateral to the uterotubal junctionin interstitial ectopic pregnancy and pregnancy in rudimentaryhorn of unicornuate uterus but it was medial to it in the other 3situations.Conclusion: Our study described a simple triaging model basedon sonographic criteria for four pregnancy situations where thegestational sac appears eccenterically in the early 1st trimester.These four situations are namely; interstitial ectopic pregnancy,ectopic pregnancy in a rudimentary horn of a unicornuate uterus,angular pregnancy and pregnancy in one sideof a septate or bicornuate uterus. This modelwill be helpful for early accurate diagnosis toavoid false positive diagnosis that may lead tounnecessary intervention and false negativediagnosis that may lead to maternal morbidityor mortality.