Differentiation between endometritis and RPOC in febrile postpartum patients is commonly requested by clinicians. Sonography is the screening technique of choice to assess the endometrial contents. For cases in which the retained placenta is calcified or still has demonstrable blood flow, a specific diagnosis of RPOC can be made. In more complicated cases, a CT scan or an MR image may be requested. In addition to evaluating the uterus and any intra- or extrauterine fluid collections, attention must be paid to the ovarian veins to exclude the diagnosis of ovarian vein thrombosis.