Retained products of conception

Retained products of conception (RPOC) refersrefer to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage. 

Epidemiology

RPOC complicatesRetained products of conception complicate ~1% of all pregnancies. It occurs with greater frequency with:

• medical termination of pregnancy (MTP) 
• second-trimester miscarriage
• placenta accreta

Clinical presentation

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 isare 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.

Radiographic features

Ultrasound

Ultrasound is typically the first-line investigation in suspected RPOCretained products of conception:

• 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 RPOCretained products of conception may be avascular ⁹
• calcifications may be present

RPOCRetained products of conception can be suspected on ultrasound if the endometrial thickness is >10 mm following dilatation and curettage or spontaneous abortion (80% sensitive).

MRI

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 

Differential diagnosis

For ultrasound appearances consider:

• blood clot within the endometrial cavity (often co-exists): non-vascular on colour Doppler ultrasound
• endometritis
• gestational trophoblastic disease
• uterine arteriovenous malformation (if prominent blood flow is present)

See also

• incomplete miscarriage