Dual blood supply to the ovaries
This illustration demonstrates the dual blood supply to the ovaries.
The main blood supply is from the ovarian artery. The second source of arterial blood comes from a collateral uterine artery.
This is important because with an ovarian torsion, there can still be some arterial vascular flow on ultrasound because of the dual blood supply. Basically, one artery can be twisted and occluded but the other can still supply blood to the ovary.
A torsion should be considered if the ovary is enlarged or edematous even if arterial flow is demonstrated.