Diagnostic Ultrasound - Abdomen and Pelvis

Retained Products of Conception
TERMINOLOGY
Abbreviations
• Retained products of conception (RPOC)
Synonyms
• Retained trophoblastic tissue
• Retained placenta
• Placental polyp
Definitions
• Retained placental tissue
○ Occurs after delivery or termination of pregnancy
IMAGING
General Features
• Best diagnostic clue
○ Thickened endometrial echo complex or echogenic
endometrial mass plus internal vascularity
– Vascularity + endometrial mass = high positive
predictive value for RPOC
□ Less likely to be RPOC if endometrial echo complex
< 10 mm in thickness and sonographically avascular
– Vascularity often low-resistance, high-velocity flow
Ultrasonographic Findings
• Grayscale ultrasound
○ Thickened endometrial echo complex > 10 mm
○ Solid, heterogeneous, or echogenic endometrial or
intrauterine mass
– Sensitivity of this finding is variable: 29-79%
○ Irregular interface between endometrium and
myometrium
○ Intrauterine fluid common
• Pulsed Doppler
○ Pulsed Doppler may show high-velocity, low-resistance
flow
– Peak systolic velocity varies but can be as high as 100
cm/sec
• Color Doppler
○ Presence of vascularity in thickened endometrial echo
complex or mass substantially increases likelihood of
RPOC (PPV 96%)
○ Degree of vascularity may range from hypovascular to
markedly hypervascular compared to normal uterine
myometrium
– Pitfalls
□ Markedly hypervascular RPOC may mimic
arteriovenous malformation (AVM)
□ Avascular RPOC may mimic clot
CT Findings
• CECT
○ Intrauterine endometrial mass with variable contrast
enhancement
MR Findings
• T1WI C+
○ Intrauterine soft tissue mass with variable contrast
enhancement
– No extrauterine invasion
Imaging Recommendations
• Best imaging tool
○ Grayscale and color Doppler ultrasound for evaluation of
uterus and detection of internal vascularity
○ MR for problem solving is occasionally necessary
DIFFERENTIAL DIAGNOSIS
Normal Postpartum Uterus
• Highly variable, from smooth to irregular endometrium
• Small echogenic foci and fluid common
• Foci of gas may be seen in up to 21% in 1st 3 weeks post
partum
• Endometrial thickness < 2 cm initially and should decrease
to < 8 mm with uterine involution
Uterine Atony
• Primary differential consideration for immediate
postpartum hemorrhage (PPH)
• Should not see any sonographic evidence of retained
products within endometrial cavity
○ Blood/clot may potentially be confusing
Intrauterine Blood/Clot
• No flow with color Doppler
• Changes or resolves on follow-up scans
Endometritis
• Clinical diagnosis
• Postpartum fever and pelvic pain
• May see gas in endometrium but findings are typically
nonspecific
• Patient may have both RPOC and coexisting endometritis
Invasive Molar Pregnancy
• Benign tumor arising from myometrial invasion of
hydatidiform mole
• 10-17% of hydatidiform moles result in invasive moles
• Heterogeneous cystic and solid placental mass with
hypervascular components in invasive mole
• Persistently elevated beta hCG levels
• May have extrauterine extension (metastasize to lungs or
vagina)
• Chemosensitive
Arteriovenous Malformation (AVM)
• Marked vascularity isolated to myometrium
○ Vascularity should not extend to endometrium in uterine
AVM
○ No tissue in endometrial cavity
○ Hypervascular RPOC often misdiagnosed as uterine AVM
○ Enhanced myometrial vascularity (a.k.a. uterine non-
AVM) can have similar appearance
• Most develop secondary to uterine tissue injury, most
commonly from prior D&C for termination of pregnancy
• Serum beta-hCG is usually negative or minimal
• Potential risk of life-threatening hemorrhage
• Definitive diagnosis made by identification of early draining
vein on angiography
• True incidence of AVM unknown
Subinvolution of Placental Implantation Site
• Idiopathic cause of postpartum hemorrhage
Diagnoses: Female Pelvis
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