Torsion, or a twist of the ovary around its pedicle, leads to venous stasis, edema, and eventual ischemia. Although isolated ovarian torsion does occur, usually it is associated with fallopian tube torsion. It can occur during pregnancy. An ovarian cyst or other tumor, regardless of etiology, predisposes to torsion (gynecologists and urologists prefer the terms severe torsion or even simply torsion to what gastroenterologists would label as volvulus for an equivalent condition in the gut).
Ovarian torsion occurs most often in girls and young women but has developed in neonates. Depending on the degree of twist, the onset of pain ranges from gradual to sudden. Severe pain is a common presentation of complete torsion. Clinically, acute right ovarian torsion mimics appendicitis. A not uncommon scenario consists of acute appendicitis being suspected in a young girl, but subsequent laparotomy detects a torsed and necrotic ovary.
Chronic partial ovarian torsion is rare. Intermittent venous obstruction and edema result in massive ovarian enlargement. Neglected amputated ovaries secondary to ovarian torsion can evolve into calcified cystic tumors which became attached to adjacent structures by a pedicle containing vessels. Salpingo-oophorectomy is often performed for ovarian torsion. Occasionally prophylactic oophoropexy or even laparoscopic shortening of the uteroovarian ligament is feasible for intermittent torsion.
Imaging shows a large, irregular adnexal tumor ranging from solid to thick-walled and cystic. Any cystic component, when present, represents engorged follicles. Some hemorrhage is common and, if untreated, eventual necrosis ensues. Echogenicity of a torsed ovary varies considerably.
A US finding of a twisted vascular pedicle is suggestive of ovarian torsion but this is not always present. Doppler US suggests the degree of viability of a torsed ovary.With a nonviable ovary, Doppler US shows absent arterial and venous flow centrally, low-velocity arterial flow in the periphery, or absent or even reversed diastolic arterial flow. The lack of blood flow within a twisted vascular pedicle implies a nonviable ovary. The presence of internal arterial flow has prognostic implications because some of these can be treated successfully with laparoscopic untwisting.
Occasionally US detects an engorged fallopian tube. Cul-de-sac fluid is a common but nonspecific finding. Ultrasonography is not foolproof, however. Transabdominal US in two girls with abdominal cysts revealed a “double wall” sign, and duplication cysts were diagnosed; surgery revealed ovarian cysts, torsion,and hemorrhage within the cyst wall.
In addition to detecting engorged blood vessels in ovarian torsion, MR often also detects uterine deviation to the twisted side. The lack of CT or MRI contrast enhancement of the involved ovary signifies arterial compromise. The wall of any associated cystic tumor is edematous and thickened.Any superimposed hemorrhage modifies the imaging appearance. A rare finding with torsion involving an ovarian tumor is presence of intravascular gas within the tumor. This gas probably represents oxygen released from trapped oxyhemoglobin.
This is radiology images of the ovarian torsion in an 11-year-old girl with pelvic pain. Computed tomography reveals a retrovesical tumor. Normal gynecological structures were not identified. An appendiceal abscess was initially suspected.
This is utrasound images of the ovarian torsion. A: US in a young girl with suspected appendicitis identified a normal appendix (cursors). B: Further pelvic US detected a tumor in the pouch of Douglas and cul-de-sac. Surgery revealed a left fallopian tube and ovary torsed 720 degrees.