Diagnostic Ultrasound - Abdomen and Pelvis

Failed First Trimester Pregnancy
Diagnoses: Female Pelvis
Pregnancy of Unknown Location (PUL)
• Positive pregnancy test with no signs of intra- or
extrauterine pregnancy on US
• Usually IUP when hCG > 2000 mIU/mL IRP
○ hCG 3000 mIU/mL, viable IUP is unlikely, most likely
diagnosis is nonviable IUP → follow-up hCG and US if
increasing
– hCG falls to zero with complete abortion
Retained Products of Conception (RPOC)
• Disorganized echogenic material in uterine cavity
• Color Doppler shows hypervascular pattern within
endometrial contents
• Retained clot is usually hypoechoic, nonperfused
• No recognizable gestational sac
Gestational Trophoblastic Disease (GTD)
• Classic hydatidiform mole has "cluster of grapes"
appearance
• May see abnormal-appearing gestational sac
○ Can mimic anembryonic sac
• Associated with ovarian theca lutein cysts
Cervical Ectopic Pregnancy
• Eccentric GS in wall of cervix; closed cervical os
• Cardiac activity more suggestive of cervical ectopic
• Passing abortion: Centrally located contents ± open internal
os; may move during examination or on follow-up US
PATHOLOGY
General Features
• Etiology
○ 60% of spontaneous abortions < 12 weeks due to
abnormal chromosomes
○ Less commonly: Uterine abnormalities, maternal
infection, alcohol, smoking, immunologic and genetic
defects
Microscopic Features
• Chorionic villi present in uterine curettings
○ Significant reduction in number of vessels per chorionic
villus and abnormally located vessels suggests
inadequate vasculogenesis
• Nuclear DNA abnormal in up to 40%
○ Suggests chromosomal aberrations → abnormal
embryogenesis → anembryonic gestation
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Vaginal bleeding, pelvic pain, uterine contractions
– May be heavy with incomplete or complete abortion
○ May be asymptomatic and diagnosed during routine US
○ Patient perception of diminished pregnancy symptoms
• Laboratory results
○ hCG > 3,000 mIU/mL IRP and no IUP
– Failing IUP vs. early multiple gestation vs. EP
○ Lower hCG level and IUP not seen
– Viable or nonviable IUP vs. EP
○ Obtain follow-up hCG and US in indeterminate cases
– hCG levels double every 2-3 days with normal IUP
– Dropping levels suggest failing pregnancy
○ Maternal serum progesterone levels
– Helps predict normal IUP vs. EP/failing IUP
– Cannot differentiate EP from failing IUP
– < 5 ng/mL = nonviable pregnancy in 100%
– > 25 ng/mL excludes ectopic with 97.5% sensitivity
Demographics
• Epidemiology
○ 30-60% documented hCG elevations end as failed
pregnancy
○ Up to 20% of confirmed early pregnancies end in
spontaneous abortion
– 35% anembryonic, 54% early loss (cause not
specified), 11% molar (partial or complete)
○ Groups with ↑ incidence of early pregnancy failure
– Advanced maternal age; poor diabetic control; history
of recurrent abortions
Natural History & Prognosis
• Threatened abortion → 1/2 abort
• Risk decreases to 5% if living embryo seen on US
• Random event with no specific recurrence risk if isolated
• Patients with recurrent abortion may be treated with
aspirin, heparin, or progesterone supplementation (for
luteal phase insufficiency)
Treatment
• "Wait and see" → most will pass without treatment
• Vaginal misoprostol
○ Many patients prefer definitive treatment to expectant
management
○ Successful evacuation of uterus in majority of patients
○ Some will require curettage, but overall expect 50%
reduction in need for surgical management
• Suction curettage
○ Small associated risk of excessive bleeding, uterine
rupture, Asherman syndrome
DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Empty amnion + MSD ≥ 25 mm → anembryonic gestation
• Lack of cardiac activity and CRL ≥ 7 mm → embryonic
demise
• Be cautious when categorizing nonspecific intrauterine
fluid collection as pseudosac
○ Nonspecific intrauterine fluid collection is more likely to
be GS than pseudosac
○ Make diagnosis of ectopic pregnancy with definitive
signs, not by lack of IUP, to minimize risk of harming IUP
SELECTED REFERENCES
1. Doubilet PM: Ultrasound evaluation of the first trimester. Radiol Clin North
Am. 52(6):1191-9, 2014
2. Doubilet PM et al: Diagnostic criteria for nonviable pregnancy early in the
first trimester. N Engl J Med. 369(15):1443-51, 2013
3. Lane BF et al: ACR appropriateness Criteria® first trimester bleeding.
Ultrasound Q. 29(2):91-6, 2013
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