Follicular ring sign

The follicular ring sign is considered as a characteristic sonographic sign for early diagnosis of ovarian torsion . It is defined as prominent (1-2 mm thick) hyperechoic margin seen concentrically around the antral follicles of the torsed ovary, which are usually small (3‐ to 7‐mm) and peripherally displaced.

The antral follicles in normal ovaries, can sometimes have hyperechoic margins due to acoustic enhancement, but they are imperceptible and not seen all around the follicle.