Retained products of conception
Retained products of conception (RPOC) refers to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage.
RPOC complicates ~1% of all pregnancies. It occurs with greater frequency with:
Common symptoms include vaginal bleeding and abdominal or pelvic pain, similar to patients with gestational trophoblastic disease.
Differentiation of these entities is important because retained products of conception is 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 RPOC:
- variable amount of echogenic or heterogeneous material within the endometrial cavity
- presence of vascularity within the echogenic material supports the diagnosis but the absence of color Doppler flow has a low negative predictive value because RPOC may be avascular 9
- calcifications may be present
RPOC can be suspected on ultrasound if the endometrial thickness is >10 mm following dilatation and curettage or spontaneous abortion (80% sensitive).
Retained products of conception can appear on MR imaging as an intracavitary uterine soft-tissue mass with variable amounts of enhancing tissue and variable degrees of myometrial thinning and obliteration of the junctional zone.
Signal characteristics include:
- T1: variable heterogeneous signal 1
- T2: variable heterogeneous signal 1
- T1 C+ (Gd): can show variable enhancement
For ultrasound appearances consider:
- blood clot within the endometrial cavity (often co-exists): non-vascular on color Doppler ultrasound
- gestational trophoblastic disease
- uterine arteriovenous malformation (if prominent blood flow is present)