Sonography of uterine abnormalities in postpartum and postabortion patients: a potential pitfall of interpretation

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.

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.

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.

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.