Retained products of conception
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Retained products of conception (RPOC) refer to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage.
RPOC complicates ~2.5% (range 1-5%) of all routine vaginal deliveries 12.
According to one prospective study, RPOC was present after a third-trimester delivery in ~3% of women, whereas it was diagnosed in pregnancies ending during the second and first trimesters in 40% and 17% respectively 12.
It occurs with greater frequency with:
Common symptoms include vaginal bleeding and abdominal or pelvic pain, similar to patients with gestational trophoblastic disease. Some patients may have a fever 11.
Differentiation of these entities is important because retained products of conception are treated conservatively or with curettage, while gestational trophoblastic disease may require chemotherapy.
ß-human chorionic gonadotropin (beta-hCG) remains elevated in patients with gestational trophoblastic disease but falls to an undetectable level over 2-3 weeks, in cases of retained products.
Ultrasound is typically the first-line investigation in suspected retained products of conception:
a variable amount of echogenic or heterogeneous material within the endometrial cavity
in some instances, this may present as an endometrial or intrauterine mass
presence of vascularity within the endometrial echogenic material supports the diagnosis but the absence of color Doppler flow has a low negative predictive value because retained products of conception may be avascular 9
calcification may be present
Retained products of conception can be suspected on ultrasound if the endometrial thickness is >10 mm following dilatation and curettage or spontaneous abortion (80% sensitive) 13. Furthermore, if the endometrial thickness is less than 10 mm, there is a relatively high negative predictive value (63-80%) for RPOC 13.
Three vascularity patterns have been established on Doppler ultrasound 12:
type 1: minimal endometrial vascularity less than the myometrium
type 2: moderate vascularity with nearly equal endometrial and myometrial vascularity
type 3: marked endometrial vascularity more than adjacent myometrium
arterial flow velocities >100 cm/sec can occur with low-resistance spectral waveform and large vessels present, potentially mimicking a uterine arteriovenous malformation
MRI appearance of intrauterine soft tissue is variable depending on the degree of hemorrhagic or necrotic components 13. There may be a variable degree of associated myometrial thinning and obliteration of the junctional zone.
Signal characteristics include 1:
T1: variable heterogeneous signal
T2: variable heterogeneous signal
T1 C+ (Gd): variable enhancement
For ultrasound appearances consider:
normal postpartum appearance
blood clot within the endometrial cavity (often co-exists): non-vascular on color Doppler ultrasound
uterine arteriovenous malformation: more prominent blood flow is present; usually centered in the myometrium 12