Diagnostic Ultrasound - Abdomen and Pelvis

Unusual Ectopic Pregnancies
Diagnoses: Female Pelvis
TERMINOLOGY
• Interstitial ectopic pregnancy (EP): Pregnancy occurring in
intramural portion of fallopian tube
• Cornual EP: Pregnancy in cornua of an anomalous uterus
• Uterine scar EP: Implantation of pregnancy at site of
previous uterine surgery
• Cervical EP: Gestational sac (GS) in wall of the cervix
• Ovarian EP: GS implanted on ovary
• Abdominal EP: Implantation in peritoneal cavity
• Heterotopic pregnancy: Concurrent intrauterine and
ectopic pregnancies
IMAGING
• Best diagnostic clues on ultrasound (US)
○ Interstitial: Interstitial line sign = echogenic line from
endometrium to ectopic sac
○ Cornual: Occurs with uterine mullerian duct anomaly
○ Scar EP: Eccentrically located GS at site of C-section scar
○ Cervical EP: GS eccentric to the endocervical canal
KEY FACTS
• 3D ultrasound: Improves visualization of gestational sac in
relation to the intrauterine cavity
• MR: Reserved for problem solving when US findings are
equivocal or preoperative planning for large ectopics
TOP DIFFERENTIAL DIAGNOSES
• Intrauterine pregnancy vs. interstitial or scar EP
• Tubal ectopic vs. interstitial EP
• Septate uterus vs. interstitial EP
• Abortion in progress vs. cervical EP
• Corpus luteum vs. ovarian EP
CLINICAL ISSUES
• Overall, increased morbidity and mortality compared to
usual tubal EP
○ Improved blood supply in setting of unusual EP often
allows GS to grow larger and present later
• Diagnosis of unusual ectopic pregnancy can be difficult;
must have a high degree of suspicion, especially in a highrisk
patient
(Left) Transverse transvaginal
US of an interstitial EP shows
an eccentrically located GS
with a fetal pole
protruding from the lateral
aspect of the uterus, separate
from the empty endometrial
cavity ſt. Note thinned
overlying myometrium st.
(Right) Longitudinal
transvaginal ultrasound of a
cervical EP shows an empty
uterus ſt with a round,
eccentrically located
gestational sac in the
anterior wall of the cervix.
Note thin central curved line
of the endocervical canal st
and fetal pole .
(Left) Longitudinal
transvaginal US of a cesarean
section scar ectopic, shows an
eccentrically located gestation
sac within the lower
anterior uterine myometrium
at the site of a cesarean
section scar ſt. Note the yolk
sac and fetal pole and
empty endometrial cavity st.
(Right) Longitudinal
transvaginal US shows an
abortion in progress with a
centrally located, tear-drop
shaped gestational sac
spanning the lower uterine
cavity and endocervical canal.
Note wide open internal os st
and fetal pole ſt.
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