|Arteries of the female reproductive tract: uterine artery, ovarian artery and vaginal arteries. (Ovary and ovarian artery visible in upper right.)|
|Classification and external resources|
Ovarian torsion accounts for about 3% of gynecologic emergencies. The incidence of ovarian torsion among women of all ages is 5.9 per 100,000 women, and the incidence among women of reproductive age (15–45 years) is 9.9 per 100,000 women. In 70% of cases, it is diagnosed in women between 20 and 39 years of age. The risk is greater during pregnancy and in menopause. Risk factors include increased length of the ovarian ligaments, pathologically enlarged ovaries (more than 6 cm), ovarian masses or cysts, and enlarged corpus luteum in pregnancy.
The development of an ovarian mass is related to the development of torsion. In the reproductive years, regular growth of large corpus luteal cysts are a risk factor for rotation. The mass effect of ovarian tumors is also a common cause of torsion. Torsion of the ovary usually occurs with torsion of the fallopian tube as well on their shared vascular pedicle around the broad ligament, although in rare cases the ovary rotates around the mesovarium or the fallopian tube rotates around the mesosalpinx. In 80%, torsion happens unilaterally, with slight predominance on the right.
Ovarian torsion is difficult to diagnose accurately, and operation is often performed before certain diagnosis is made. A study at an obstetrics and gynaecology department found that preoperative diagnosis of ovarian torsion was confirmed in only 46% of patients. Gynecologic ultrasonography is the imaging modality of choice.
Lack of ovarian blood flow on Doppler sonography seems to be a good predictor of ovarian torsion. Women with pathologically low flow are more likely to have OT (77% vs. 29% in a study). The sensitivity and specificity of abnormal ovarian flow for OT are 44% and 92%, respectively, with a positive and negative predictive value of 78% and 71%, respectively. Specific flow features on Doppler sonography include:
- Little or no intra-ovarian venous flow. This is commonly seen in ovarian torsion.
- Absent arterial flow. This is a less common finding in ovarian torsion
- Absent or reversed diastolic flow
Normal vascularity does not exclude intermittent torsion. There may occasionally be normal Doppler flow because of the ovary's dual blood supply from both the ovarian arteries and uterine arteries.
Other ultrasonographic features include:
- Enlarged hypoechogenic or hyperechogenic ovary
- Peripherally displaced ovarian follicles
- Free pelvic fluid. This may be seen in more than 80% of cases
- Whirlpool sign of twisted vascular pedicle
- Underlying ovarian lesion can often be found
- Uterus may be slightly deviated towards the torted ovary.
The use of plasma D-dimer level has been studied in the diagnosis of torsion. With a cut-off value 0.65 mg/ml, the sensitivity in determining adnexal/ovarian torsion was found to be 71.4%. Specificity was 85%.
Surgical treatment of ovarian torsion includes laparoscopy to uncoil the torsed ovary and possibly oophoropexy to fixate the ovary which is likely to twist again. In severe cases, where blood flow is cut off to the ovary for an extended period of time, necrosis of the ovary can occur. In these cases the ovary must be surgically removed.
- Testicular torsion – equivalent condition of the male reproductive system
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- Ovarian Torsion at eMedicine
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