Sonography of Uterine Abnormalities in Postpartum and Postabortion Patients

OBJECTIVE: The interpretation of postpartum and postabortion uterine abnormalities on sonography can be challenging. The purpose of this study was to identify misleading imaging features that lead to inclusion of a uterine arteriovenous malformation (AVM) in the differential diagnosis of a uterine abnormality because consideration of this diagnosis can potentially alter patient treatment. METHODS: The sonographic examinations of 29 pathologically proven cases of uterine abnormalities in postpartum and postabortion patients were retrospectively reviewed. Two radiologists independently evaluated several features: the presence of a uterine mass, myometrial involvement, and the presence of an associated vascular abnormality. Percent agreement and the relationship between imaging features and inclusion of a uterine AVM in the differential diagnosis were determined. RESULTS: Interobserver agreement was as follows: the presence of a uterine mass, 90%; myometrial involvement, 83%; the presence of an associated vascular abnormality, 72%; and inclusion of a uterine AVM in the differential diagnosis, 86%. Myometrial involvement showed a statistically significant relationship to inclusion of a uterine AVM in the differential diagnosis (P < .05). Final pathologic diagnoses included retained products of conception (RPOC) (n = 26), an endometrial polyp (n = 1), chronic endometritis (n = 1), and an exogenous progestational effect (n = 1). No uterine AVMs were found. CONCLUSIONS: Despite high interobserver agreement in characterizing uterine abnormalities on sonography, readers still include uterine AVMs in the differential diagnosis of uterine masses that are ultimately proven to be RPOC. A myometrial location of a uterine mass is a particularly misleading imaging feature of RPOC.