Arcuate vessels are commonly seen on ultrasound evaluation of the uterus. Occasionally they can be confused with subchorionic hemorrhage, ovaries, and other structures so it’s worth looking at their characteristic appearance.
Once again, thanks to Dr. Gray for his lovely, copyright-free images:
Here we see the Uterine venous plexus giving rise to the helicine branches, aka arcuate vessels. They run circumstantially through the outer margin of the myometrium.
In the images below, anechoic areas are visible in the posterior aspect of the myometrium (arrows in top two images). The bottom two images reveal the same structures with and without color flow, demonstrating their vascularity. These vessels are normal anatomic variations, and can become more engorged during pregnancy as uterine bloodflow increases.
This is again visible posteriorly in this video of a gravid uterus: