Retained products of conception mimicking a large endometrial AVM: complete resolution following spontaneous abortion

We report an unusual appearance of retained products of conception that mimicked an arteriovenous malformation. A 38-year-old woman presented with persistent scant vaginal bleeding and declining levels of serum beta-HCG after therapeutic abortion. Sonographic examination revealed a highly vascular lobulated mass, which on spectral Doppler examination showed low resistance and high peak systolic velocity suggestive of arteriovenous shunting. The patient spontaneously passed tissue per vagina, after which the endometrial vascular mass completely disappeared, indicating that the sonographic abnormality was the retained products of conception. The pathologic basis for such a finding is discussed.