Etiology
Underlying anatomic abnormalities account for the highest percentage of patients. Specifically, cysts and neoplasms (both benign and malignant) account for >90% of all cases of adnexal torsion, and the remainder occur in normal-appearing ovaries.[4] Neoplasms account for 46% of anatomic abnormality-related cases, and cysts make up the rest.[4] The likelihood of a malignancy is greater in postmenopausal women. Most cases of ovarian torsion (>90%) are found to be due to benign causes.[4][12][13]
The size of the ovary seems to be a strong factor in the likelihood of torsion.[14] The larger the ovary, the greater the chance for torsion. However, there is no absolute size that precludes or induces torsion. In children who experience torsion, up to 50% of all cases occur in normal-sized ovaries with no anatomic abnormalities.[4][15][16]
Torsion in the presence of normal ovaries has been attributed to an abnormally long fallopian tube, mesosalpinx, or mesovarium; adnexal venous congestion due to constipation; sigmoid distention; pregnancy; premenarchal hormonal activity; or a significant jarring motion.[17] Sudden increased abdominal pressure, such as from coughing, hiccupping, defecation, and vomiting, may push the ovary to rotate on its pedicle.[14] Torsion is more likely to be found on the right side than on the left side, in a ratio of about 3:2.[18]
Pathophysiology
Enlargement of the ovary allows it to rotate on its pedicle around its ligamentous supports.[19] This twisting of the vasculature impedes blood flow to the ovary, and possibly the fallopian tube. Total blockage may result in ischemia, necrosis, and hemorrhage.[19] This eventually may result in peritonitis and systemic infection.
In general, the venous outflow is compromised to a greater degree than arterial inflow, as the vein walls are significantly thinner and more easily compressed. This allows continued arterial perfusion and may cause enlargement and edema of the ovary.[19]
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