Diagnostic Ultrasound - Abdomen and Pelvis

Unusual Ectopic Pregnancies
TERMINOLOGY
Definitions
• Interstitial ectopic pregnancy (EP): Preferred term for
pregnancy occurring in interstitial (intramural) portion of
fallopian tube
○ Synonym: Intramural ectopic pregnancy
• Cornual EP: Often used interchangeably with interstitial
ectopic; more appropriately applied to pregnancy in the
cornua of an abnormal uterus (horn of uni- or bicornuate
uterus or lateral half of septate uterus)
• Angular pregnancy: Pregnancy implanted at lateral angle
of uterine cavity by ostium, medial to interstitial tube
• Uterine scar EP: Implantation of pregnancy at the site of
previous uterine surgery, e.g., myomectomy or cesarean
section (C-section)
○ Synonyms: Scar EP, C-section scar EP
• Cervical EP: Gestational sac (GS) implanted in the wall of
the cervix below the level of the internal cervical os
• Ovarian EP: Intraovarian implantation of a GS
• Abdominal EP: Implantation in the peritoneal cavity
○ Primary: Direct peritoneal implantation; secondary: Reimplantation
of ruptured extrauterine pregnancy in
peritoneal cavity (more common than primary form)
• Heterotopic pregnancy: Concurrent intrauterine and
ectopic pregnancies
IMAGING
General Features
• Best diagnostic clues
○ 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
• Size
○ Generally larger than tubal EP
• Location
○ Vast majority of EP occurs in the fallopian tube (95-99%):
Ampullary, isthmic, or fimbriated portions
○ Unusual locations: Interstitial/intramural portion of tube,
myometrial scar, wall of cervix, ovary, abdominal cavity
Ultrasonographic Findings
• Interstitial EP: GS eccentrically located in myometrium of
uterine fundus separate from endometrium
○ Interstitial line sign: Thin echogenic line representing
interstitial portion of the tube extending from the
ectopic GS to cornua of empty endometrial cavity
○ More commonly, see separation between echogenic
border of endometrium and outer echogenic edge of GS
○ GS with thinned overlying myometrium (< 5 mm)
– Bulge of outer contour or serosa of myometrium
– GS: Can be large ± YS or embryo; or may appear as an
echogenic mass (trophoblastic tissue and hematoma)
○ 3D ultrasound (US): Improves ability to localize GS and
visualize intramural portion of the fallopian tube
○ Doppler findings: Highly vascular trophoblastic tissue
– May see prominent arcuate vessels in outer third of
myometrium
– Pulsed Doppler: High-velocity, low-resistance
waveform
• Cornual EP: Eccentrically located with similar appearance to
interstitial pregnancy but in anomalous uterus
○ Visualization of uterine anomaly necessary for diagnosis
○ 3D US: Improves visualization of uterine cavity and
fundus in order to diagnose congenital uterine
anomalies and location of GS
• Angular pregnancy: GS located in the uterine cavity
deviated towards the lateral angle with thin overlying
myometrium
○ 3D US: Improves visualization of the gestational sac in
relation to the intrauterine cavity
○ GS may descend into the endometrial cavity on
subsequent studies
• Scar EP: GS located in the anterior myometrium of the
lower uterine segment eccentric to the endometrium, in
patient status-post C-section
○ Myometrium between bladder and GS: Thinned or
absent
○ Triangular configuration of C-section scar at implantation
site; possibly with fluid along edge
○ Sac may extend into endometrial cavity or beyond
serosal surface of the uterus
• Cervical EP: GS in the wall of the cervix, adjacent to
endocervical canal; closed internal os
○ Later presentation → hourglass-shaped uterus: Uterine
body = top of hourglass, bulging cervical EP = bottom,
waist = level of internal os
○ Color Doppler: Peritrophoblastic perfusion ± feeding
vessel from the cervical wall
• Ovarian EP: GS (± YS &/or embryo) surrounded by ovarian
parenchyma
○ Moves with the ovary when gentle pressure applied
during TV examination
○ Very difficult to diagnose by ultrasound; most cases
diagnosed intraoperatively
• Abdominal EP: EP at site of pain outside adnexa
○ May be best seen transabdominally
• Heterotopic pregnancy: Consider in patient undergoing
assisted reproduction
○ Can be tubal, interstitial, scar, cervical, or less commonly
ovarian or abdominal
MR Findings
• GS: Eccentric, thick-walled cystic structure with T2
hyperintense wall
○ Separated from endometrium by junctional zone in
interstitial pregnancy and scar EP
• Corpus luteum: Wall shows low T2 signal intensity
• Associated hematoma: Intermediate to high signal on T1
and low T2 signal
Imaging Recommendations
• Always document location of sac with respect to
endometrium in both transverse and longitudinal planes
• Measure surrounding myometrium if it appears thin
• Use 3D ultrasound if available
○ High concordance between 3D US and MR; and more
rapid access and lower cost
• If diagnosis is unclear: MR or short term follow-up
• Target transabdominal US to area of pain if outside adnexa
Diagnoses: Female Pelvis
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