KEY FACTS
Imaging
- •
Interstitial ectopic : Implantation in portion of tube crossing myometrium at cornua of uterus
- ○
Eccentrically located with respect to endometrial cavity
- ○
Bulges cornua of uterus
- ○
< 5 mm of surrounding myometrium very suggestive
- ○
Interstitial line sign: Echogenic line from endometrium to ectopic sac
- ○
3D ultrasound shown to improve diagnosis and should be performed in every suspected case
- ○
Covered by myometrium so can grow to larger size than tubal ectopic; catastrophic bleeding if ruptures
- ○
- •
Cervical ectopic
- ○
Within cervical stroma separate from endocervical canal
- ○
Hourglass-shaped uterus: Cervical distention from pregnancy, with “waist” due to closed internal os
- ○
Primary differential is spontaneous abortion
- –
Irregular, deformed, flattened sac in cervical canal
- –
- ○
- •
Cesarean scar ectopic
- ○
Sac will be below midpoint of uterus within anterior myometrium at site of C-section scar
- ○
Must evaluate overlying myometrium
- –
Deep implantation into defect, risk of impending rupture and life-threatening bleeding
- –
Sac protruding into uterine cavity can lead to live birth but all will have placenta accreta
- –
- ○
- •
Abdominal ectopic
- ○
Most often implants on uterus or in posterior cul-de-sac
- ○
May present quite late as not in contained space (e.g., fallopian tube), which would rupture
- ○
Membranes form sac around embryo/fetus and may be mistaken for myometrium
- ○
- •
Ovarian ectopic
- ○
Vascular echogenic ring in ovary far more likely to be corpus luteum cyst
- ○
More echogenic and rounder than typical corpus luteum
- ○
Location on/near surface of ovary
- ○
. The coapted margins of the interstitial portion of the tube create the interstitial line sign 
. Cornual pregnancy is often used interchangeably, but there are inconsistent definitions, and this term should be dropped.
with no clear myometrial covering. An interstitial line sign 
connects empty endometrial cavity 
to sac.
clearly separate from the endometrial cavity 
. 3D US is the best way to make this diagnosis and should be performed in all suspected cases. Note the claw of myometrium 
, which becomes imperceptibly thin along the fundal border of the sac. Rupture can lead to catastrophic bleeding.
.
is closed. The bladder neck 
is a landmark for the level of the internal os. The oval gestational sac 
, which contains a yolk sac, is clearly implanted in the cervix, not the uterine cavity.
