Retained Products of Conception
Synonyms/Description
RPOC
Retained placenta
Incomplete abortion
Etiology
Retained products of conception (RPOC) may occur following an abortion, a vaginal delivery, or even after a Cesarean section. This obstetric complication most commonly results in prolonged or excess vaginal bleeding and has also been associated with endometritis. The retained tissue may include a portion of the placenta (such as a succenturiate lobe) or tissue from a pregnancy not completely evacuated.
Ultrasound Findings
Retained products of conception typically appear as an echogenic, vascular mass with ill-defined borders, centrally located within the endometrial cavity. The mass may contain areas of fluid but is largely solid. Color Doppler often shows an alarming amount of vascularity, which has been described as mimicking an arteriovenous malformation (AVM); however, this resolves completely after evacuation of the retained products. The sonographic appearance of the retained tissue can have characteristics of placenta, especially if the patient is postpartum. If the patient had an early pregnancy loss or termination, the tissue is more often echogenic with small cystic areas. Abundant vascularity is a characteristic feature of most types of retained products of conception.
Durfee and colleagues report that an endometrial mass is the most sensitive (79%) and specific (89%) sonographic finding in patients with retained products of conception. None of the patients in their study with this diagnosis had a completely normal scan.
Regarding vascularity, Atri and colleagues report that the presence of focal vascularity had sensitivity, specificity, negative predictive value, and positive predictive value of 94%, 67%, 95%, and 65%, respectively. Of the patients with pathologically confirmed retained products of conception, five had focal increased vascularity without a mass, but none had a mass without focal increased vascularity.
Differential Diagnosis
When observing a vascular mass in the endometrium, it is important to determine the clinical history. The sonographic appearance alone may suggest a large polyp or an abnormal endometrium such as hyperplasia or endometrial cancer. If the vascularity in the lesion is dramatic, an AVM may be suspected, although primary uterine AVMs are exceedingly rare. If the patient is postpartum or if there has been a recent pregnancy loss, the diagnosis is retained products of conception until proved otherwise.
Clinical Aspects and Recommendations
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