Ovarian Torsion
Ovarian torsion occurs when an ovary twists on the ligaments that suspend it, cutting off its own blood supply. It is a surgical emergency: without prompt treatment the ovary becomes starved of blood and can be permanently lost. It usually happens to an ovary that has been enlarged by a cyst or other mass, which gives it enough weight and mobility to rotate. The classic presentation is sudden, severe, one-sided pelvic pain, often with nausea and vomiting—but the picture is frequently less clear-cut than that, with pain that comes and goes as the ovary twists and untwists, and this intermittent pattern is a common reason the diagnosis is delayed. Surgery to untwist the ovary usually saves it, even when it looks badly affected.
What is it?
Each ovary is suspended within the pelvis by two ligaments. The ovarian ligament anchors it to the uterus, and the suspensory ligament—also called the infundibulopelvic ligament—tethers it to the pelvic sidewall and carries the ovarian artery and vein. This arrangement allows the ovary a degree of mobility, which is normally harmless.
Ovarian torsion occurs when the ovary rotates around this axis, twisting the suspensory ligament and the vessels running within it. Because the fallopian tube usually twists alongside it, the condition is often more accurately described as adnexal torsion.
The sequence that follows is what makes this an emergency. The veins, being thin-walled and low-pressure, are compressed first. Blood continues to arrive through the thicker-walled artery but cannot leave, so the ovary becomes engorged and swollen. This swelling increases the pressure within the ovary and tightens the twist further, and eventually arterial inflow is also obstructed. Without blood supply, the tissue becomes ischaemic and, if the situation persists, dies.
This staged process explains several features of the condition. It explains why the ovary is characteristically enlarged and oedematous on imaging—that swelling is the trapped blood. It explains why arterial blood flow may still be detectable early on, when veins are obstructed but the artery is not. And it explains why the process is potentially reversible: untwisting the ovary restores drainage, and tissue that looks alarming can recover.
Torsion almost always affects an ovary that is abnormally heavy or enlarged. A normal ovary is small and relatively fixed, and rarely twists. An ovary containing a cyst of several centimetres has the mass and leverage to rotate. Most implicated cysts are benign—functional cysts, mature cystic teratomas, cystadenomas, and endometriomas. Dermoid cysts are particularly associated, both because they are dense and heavy and because they occur in the age group most affected.
Size matters in a non-linear way. Very small cysts rarely cause torsion, and very large masses often become too fixed within the pelvis to rotate. Masses in an intermediate range—commonly around five centimetres or more—carry the greatest risk.
Malignant masses cause torsion less often than benign ones, because cancer tends to provoke adhesions that anchor the ovary in place.
Several specific situations raise risk considerably.
Pregnancy increases risk, particularly in the first trimester and early second trimester, when the corpus luteum cyst is present and the enlarging uterus lifts the ovaries out of the pelvis into a more mobile position.
Ovarian stimulation for fertility treatment produces multiple enlarged ovaries and substantially increases risk, especially where ovarian hyperstimulation syndrome develops.
Children and adolescents can experience torsion of a normal ovary, without any cyst, thought to reflect longer ligaments and greater mobility at that age. This is an important variant because the absence of a mass can lead clinicians to dismiss the possibility.
Previous torsion increases the risk of recurrence, on the same or the opposite side.
The right side is affected more often than the left, most likely because the sigmoid colon occupies space on the left and limits movement there. This asymmetry also contributes to diagnostic confusion, since right-sided pelvic pain frequently prompts consideration of appendicitis first.
The presentation is typically dramatic but not always.
The classic picture is sudden, severe, one-sided lower abdominal or pelvic pain, often sharp, sometimes radiating to the back, flank, or thigh. It may begin after exercise, a sudden change of position, or intercourse, though it commonly occurs without any trigger, including during sleep. Nausea and vomiting accompany the pain in a majority of women and are prominent enough that the presentation is sometimes mistaken for gastroenteritis.
The less classic picture is the one that causes problems. In a substantial proportion of cases, pain is intermittent—severe for hours, then easing, then returning. This reflects the ovary twisting and partially untwisting. The danger is that a woman whose pain has settled may be reassured and sent home, or may not seek help at all, while the ovary remains at risk and can twist again. Pain that has resolved does not mean the problem has.
Fever and a raised white cell count can develop later, as tissue becomes ischaemic, and these findings can push the assessment toward infection rather than torsion.
On examination there is marked tenderness on the affected side, and a tender mass may be palpable.
The differential diagnosis is broad and accounts for much of the difficulty. It includes ruptured ovarian cyst, ectopic pregnancy, appendicitis, pelvic inflammatory disease, kidney stone, urinary infection, and gastrointestinal causes. A pregnancy test is essential in every case, since ectopic pregnancy must be excluded and pregnancy also changes management.
Diagnosis rests on clinical suspicion supported by imaging, and one point about imaging deserves particular emphasis.
Pelvic ultrasound with Doppler is the first-line test. Characteristic findings include an enlarged, oedematous ovary, often considerably larger than the other; displacement of the ovary toward the midline or to an abnormal position; small follicles pushed to the periphery of the swollen ovary, sometimes described as a string of pearls appearance; free fluid in the pelvis; and a whirlpool sign—a spiral appearance of the twisted vascular pedicle—which is the most specific finding when present.
The critical caveat is that normal Doppler blood flow does not exclude torsion. This is one of the most important practical points in this condition. The ovary has a dual blood supply, arterial flow may persist while venous drainage is obstructed, and torsion may be intermittent so that flow appears normal at the moment of scanning. Studies have repeatedly shown normal Doppler findings in surgically confirmed torsion. Torsion therefore remains a clinical diagnosis that imaging supports, and a reassuring scan in a woman with a convincing clinical picture should not close the matter.
CT and MRI may show an enlarged ovary, surrounding inflammatory change, and sometimes the twisted pedicle. CT is often performed when the initial clinical impression is appendicitis or another abdominal cause, and torsion is identified incidentally. MRI is useful in pregnancy where radiation is avoided and ultrasound is inconclusive.
Blood tests are non-specific. Inflammatory markers may be raised, particularly later, but normal results do not exclude the diagnosis.
Laparoscopy provides the definitive diagnosis and, in the same procedure, the treatment. Where clinical suspicion is high, proceeding to laparoscopy is appropriate even if imaging is equivocal, because the cost of a negative laparoscopy is far lower than the cost of a lost ovary.
Important to Know
Ovarian torsion is a time-critical condition in which the ovary can usually be saved if surgery happens promptly. Care is coordinated by gynaecologists, with emergency and paediatric surgical teams involved as relevant.
The principle that has most changed practice is that ovaries should be preserved rather than removed. Historically, an ovary that appeared dark, swollen, and apparently dead at operation was removed on the assumption it could not recover. Evidence accumulated over the past few decades has shown this assumption to be wrong: after untwisting, the great majority of such ovaries regain normal appearance, blood flow, and hormonal and reproductive function, including in ovaries that looked severely compromised. Detorsion with preservation is now the recommended approach except where tissue is frankly necrotic or malignancy is suspected.
A related historical concern also deserves correction. Untwisting was once avoided because of a fear that it would release clots causing pulmonary embolism. This complication has proven to be exceedingly rare, and the concern is no longer considered a reason to remove an ovary that could be saved.
Surgery is almost always laparoscopic, which allows the diagnosis to be confirmed, the ovary untwisted, and any cyst removed through small incisions with rapid recovery.
Removing the associated cyst at the same operation, or shortly after once the ovary has recovered, reduces the risk of recurrence. Some surgeons prefer to defer cyst removal briefly to allow oedema to settle, which can make the surgery safer and more tissue-sparing.
Fixation of the ovary—stitching it into a more stable position—is considered in specific situations: recurrent torsion, torsion of a normal ovary without any mass, and torsion in a woman with only one remaining ovary. It is not performed routinely, as the evidence for benefit in ordinary cases is limited.
Outcomes are generally good when treatment is prompt. Fertility is usually preserved, and a woman who loses one ovary typically retains normal fertility and hormonal function, since the other ovary compensates.
Delay is the main determinant of a poor outcome, and delay in this condition comes from several recognisable sources. The intermittent pain pattern leads to false reassurance. Normal Doppler findings are over-interpreted as excluding torsion. Nausea and vomiting shift attention to gastrointestinal causes. In young girls, torsion may not be considered at all, particularly in those who are not sexually active, where pelvic causes are sometimes wrongly discounted. Recognising these patterns is the most effective way to avoid losing an ovary.
In pregnancy, torsion requires the same prompt surgical treatment, and laparoscopy is safe when performed appropriately. Delaying surgery because of pregnancy increases risk to both the ovary and the pregnancy.
In children and adolescents, ovarian preservation is especially important given the reproductive years ahead. There is good evidence that ovaries in this group recover well after detorsion, and the threshold for surgical exploration should be low when torsion is suspected.
For women undergoing fertility treatment, torsion is a recognised complication, and any significant one-sided pelvic pain during or after ovarian stimulation should prompt urgent assessment rather than being attributed to expected discomfort from enlarged ovaries.
Recurrence is possible, and women who have had torsion should be aware that new severe one-sided pelvic pain warrants urgent reassessment rather than assuming it is something familiar.
Care is coordinated by gynaecology with emergency medicine, radiology, and paediatric surgery as needed. Imaging supports but does not override clinical judgement, and this is a condition where the decision to operate is often made on the overall picture rather than on any single test result.
Patient education plays an important role. Understanding that sudden severe one-sided pelvic pain warrants urgent assessment, that pain easing does not mean the problem has resolved, that a normal scan does not rule out torsion, that the ovary can usually be saved if treated quickly, and that surgery is straightforward and preserves fertility in most cases all contribute to appropriate care.
Red flag symptoms include sudden severe pain on one side of the lower abdomen or pelvis, particularly with nausea or vomiting; severe pelvic pain that comes and goes in waves; pelvic pain in a woman who is pregnant or undergoing fertility treatment; pelvic pain with a known ovarian cyst; severe pain accompanied by fever, dizziness, fainting, or a racing heart; and any severe pelvic pain in a girl or adolescent, in whom the diagnosis is frequently overlooked. These require immediate emergency assessment, as ovarian torsion is time-critical and the ovary can be lost if treatment is delayed.