Double Bladder Sign
In a female patient presenting with lower abdominal pain, abnormal ovarian (cyst) location, that is, in midline above the uterus and adjacent to urinary bladder on transabdominal scan suggests ovarian torsion. As both bladder and the cyst are anechoic structures, it appears as if there are two bladders next to each other. In addition, watch for free fluid in the pouch of Douglas.
Why talking about cyst? Note that torsion is usually associated with an ovarian cyst that twists along the infundibulopelvic ligament and pedicle, subsequently compressing the ovarian vein and artery leading to stromal edema and ovarian enlargement. Presence of the cyst is a clue to ovarian location as the ovarian tissue itself is not clearly visualized on abdominal scans. Following are 3 illustrative cases: