Solution: Ovarian torsion is the rotation of the ovary on its axis, thus producing stasis of arterial, venous, and lymphatic flow to variable degrees depending on the degree of torsion. There may be an associated mass (50-75% of the time), such as an ovarian cyst or tumor that results in the tumor, but it can be related to ovarian hypermobility as well. Occurs more often on the right than the left. Findings on imaging include: Markedly enlarged ovary, which may simply look like a mass; multiple peripheral cysts; increased through transmission (due to stromal edema); free-fluid; and "whirlpool sign" of vascular pedicle. Note that if you see a midline pelvic mass posterior to the uterus in the region of the posterior cul de sac in a young woman, your first thought should be ovarian torsion. Also note that arterial flow in the ovary does not exclude ovarian torsion for two reasons. First, partial torsion may cut of venous flow, but not arterial flow and second, there is a dual blood supply to the ovary and you may cut off one artery, but not the other. Also note that although these go to emergent surgery the ovary is not generally salvageable.