Retained products of conception (RPOC) are a common and treatable complication after delivery or termination of pregnancy.
The pathologic diagnosis of RPOC is made based on the presence of chorionic villi, which indicates persistent placental or trophoblastic tissue. In the setting of postpartum hemorrhage, however, distinguishing RPOC from bleeding related to normalpostpartum lochia or uterine atony is important. Ultrasonography is first line study in these patients. A thickened endometrium or a discrete mass in the uterine cavity is a helpful finding that suggests RPOC however detection of vascularity in a thickened endometrium or an endometrial mass at color or power Doppler US increases the positive predictive value for the diagnosis of RPOC. Diagnostic pitfalls may include highly vascular RPOC, which can be mistaken for a uterine arteriovenous malformation; true arteriovenous malformations of the uterus; invasive moles; blood clot; and subinvolution of the placental implantation site. In this lecture we explain role of different imaging modalities especially ultrasound in diagnosis, ruling out differential diagnosis and also diagnostic pitfalls.