Diagnostic Ultrasound - Abdomen and Pelvis

Tubal Ectopic Pregnancy
TERMINOLOGY
Synonyms
• Ectopic pregnancy (EP); tubal pregnancy
Definitions
• Implantation of embryo within fallopian tube
IMAGING
General Features
• Best diagnostic clue
○ No intrauterine pregnancy (IUP)
○ Heterogeneous adnexal mass separate from ovary
○ Echogenic fluid in cul-de-sac (blood)
• Location
○ 95% of EPs occur within fallopian tube
○ 75-80% ampullary, 10-15% isthmic, 5% fimbrial, 2-4%
interstitial
Ultrasonographic Findings
• Uterine findings with EP
○ Thick echogenic endometrium
– Decidual reaction
– Endometrial or decidual cysts: Can mimic intrauterine
gestational sac (GS)
○ Pseudogestational sac sign (10-20% of tubal EP)
– Teardrop-shaped fluid collection, centrally located in
endometrial cavity; surrounding echogenic decidua
– No intra- or double decidual sac sign of IUP
□ However, these signs are often absent with IUP and
not necessary for diagnosis
– Debris or clot may mimic yolk sac or embryo
○ IUP and coexistent EP extremely rare
– Greater risk (1-3%) occur with assisted reproduction
• Adnexal findings in 80-95% of tubal EP
○ Heterogeneous extraovarian mass: Most common but
least specific finding of EP
– Represents hematoma in or around EP
– Elongated, tubular configuration if in fallopian tube
– Color Doppler may show vascular ring of EP within
adnexal hematoma
○ Tubal ring sign: Echogenic ring separate from ovary (2nd
most common finding)
– With yolk sac ± embryo, increases specificity to 100%
– Usually more echogenic than ovarian stroma or corpus
luteum (CL)
– Color Doppler: "Ring of fire" = circumferential
vascularity
□ Usually incomplete ring, with focal or minimal
vascular flow
□ May help identify mass obscured by bowel or
hematoma
– Pulsed Doppler: High-velocity, low-resistance flow
• Ovary findings with tubal EP
○ CL when exophytic can mimic EP
– Thick-walled cystic structure in ovary
– Variable appearance: Anechoic → complex
hemorrhagic cyst
– Wall thicker and more hypoechoic than with EP
– Color and spectral Doppler findings overlap with EP
□ "Ring of fire" with relatively high peak systolic and
high end diastolic velocities
○ Approximately 2/3 of EP on same side as CL
• Echogenic fluid in cul-de-sac: Hemoperitoneum
○ Small amount may be seen with normal IUP
○ Larger hemoperitoneum: EP vs. ruptured CL
– Does not necessarily indicate rupture of EP
□ Retrograde bleeding/leaking from tube vs. rupture
□ Moderate or large amount hemoperitoneum,
suspect rupture
○ Clotted blood often mass-like
– Color flow may help locate hidden EP
○ May be isolated positive finding in 15% of patients
• Pregnancy of unknown location (PUL) in 5-10% of cases
○ No IUP, normal adnexa, no cul-de-sac fluid
Imaging Recommendations
• Best imaging tool
○ Transvaginal ultrasound + color Doppler
– 91% of EP accurately diagnosed
• Protocol advice
○ Correlate findings with human chorionic gonadotropin
(hCG) levels
– Usually see IUP > 2000 mIU/mL; but with no IUP, single
measurement does not reliably distinguish EP from
IUP (viable or nonviable)
– < 3000 mIU/mL presumptive treatment should not be
undertaken; risk of disrupting normal IUP
– > 3000 mIU/mL and no IUP unlikely; most likely
diagnosis is nonviable IUP → follow-up hCG and US
○ Obtain sagittal cul-de-sac view in every case to look for
echogenic blood
– May need ↑ gain settings to see echoes
– Scan abdomen when hemoperitoneum present to
assess degree
○ Color Doppler
– Can help identify small EP or EP engulfed by clot
○ Use endovaginal probe as palpation tool: "Slide test"
– EP moves independent of ovary; CL moves with ovary
○ Optimize transvaginal ultrasound (TVUS) search for yolk
sac (YS) in tubal ring; increases specificity to 100%
– Magnify image, adjust focal zone and gain, apply
pressure to anterior abdominal wall to move mass
closer to transducer, and eliminate bowel artifact
DIFFERENTIAL DIAGNOSIS
Corpus Luteum of Pregnancy
• Wall usually more hypoechoic than with EP
• Peripheral flow in wall only and tends to be more
continuous ring
• Intraovarian origin as opposed to extraovarian mass
○ "Claw" sign of ovarian parenchyma partially surrounds
exophytic CL
○ Intraovarian CL moves with ovary vs. EP, which moves
separately
Incidental Adnexal Mass
• Dermoid: Complex mass with fat, fluid, and calcification
• Neoplasm: Complex mass with nodularity, thick septations,
and vascular flow
• Paraovarian cyst
Diagnoses: Female Pelvis
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