Aetiology

Underlying anatomical abnormalities account for the highest percentage of patients. Just over half (56%) of patients in a large series of adnexal torsion had an ovarian mass, mostly with benign histology, including dermoid cysts and para-ovarian cysts.[5] The likelihood of a malignancy is greater in post-menopausal women.

The size of the ovary seems to be a strong factor in the likelihood of torsion.[13] 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 anatomical abnormalities.[6][14][15]

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 distension; pregnancy; pre-menarchal hormonal activity; or a significant jarring motion.[16] Sudden increased abdominal pressure, such as from coughing, hiccupping, defecation, and vomiting, may push the ovary to rotate on its pedicle.[13] Torsion is more likely to be found on the right side than on the left side, in a ratio of about 3:2.[17]

Pathophysiology

Enlargement of the ovary allows it to rotate on its pedicle around its ligamentous supports.[2] This twisting of the vasculature impedes blood flow to the ovary, and possibly the fallopian tube. Total blockage may result in ischaemia, necrosis, and haemorrhage.[2] This may eventually result in peritonitis.

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 causes enlargement and oedema of the ovary.[2]

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