The uterus is enlarged corresponding to 19 weeks of gestation. Within the myometrium, an ill-defined heterogeneous area is seen showing multiple serpiginous, tubular anechoic channels. On color Doppler, these channels demonstrate intense color flow with a mosaic pattern. Spectral Doppler shows high-velocity, low-resistance turbulent flow suggestive of arteriovenous shunting. No well-defined mass lesion or gestational sac abnormality is identified. Findings are consistent with uterine arterioveno