Causes and clinical presentation
This pathology most frequently occurs in patients of reproductive age. In most cases, torsion does not occur spontaneously: it is typically promoted by the presence of a benign tumor or cyst in the ovary. A dermoid cyst (mature teratoma) is a particularly common trigger, carrying the risk of not only torsion but also potential rupture or infection. Torsion may also develop against the background of pre-existing ovarian hyperstimulation syndrome (OHSS).
Clinically, patients present with acute abdominal pain, often accompanied by nausea and vomiting.
Ultrasound examination (US)
Ultrasound is the gold standard and first-line imaging method when torsion is suspected. The primary and most consistent sonographic criterion is unilateral asymmetric ovarian enlargement ($\ge$7 cm). If the organ is of normal size, the diagnosis is highly unlikely.
Additional important ultrasound signs include:
- Peripheral displacement of enlarged follicles.
- Thickening of the echogenic stroma (due to pronounced edema and internal hemorrhage).
- Abnormal location of the adnexa (they are often displaced anteriorly or posteriorly relative to the uterus).
- Deviation of the uterine body toward the affected side.
- Presence of free fluid (ascites) in the pelvic cavity.
- The specific "whirlpool" sign (whirled vascular pedicle sign) — visualization of the twisted vascular pedicle.
Color Doppler mapping (CDM) typically shows an absence of vascular signals, though it is important to remember that vascularity can be variable.
Role of CT and MRI
Computed tomography and magnetic resonance imaging are not routinely used to establish this diagnosis, but signs of torsion may be discovered during scans performed for other indications or in complex clinical cases. CT and MRI findings are often nonspecific and include a large adnexal mass (adnexal mass), ascites, and deviation of the uterus toward the affected side.
MRI (especially on T2-weighted images) allows for detailed visualization of:
- The swirl sign (swirl sign) — the twisted pedicle.
- The beaking sign (beaking sign) — wedge-shaped deformation of the ovarian mass itself.
- Peripherally displaced follicles (high signal intensity on T2-WI) against the background of stroma with increased T2 signal.
Lack of contrast enhancement (when intravenous contrast is used) within the mass reliably indicates impaired perfusion.
Differential diagnosis
Torsion must often be differentiated from other conditions accompanied by ovarian enlargement.
| Sign | Ovarian torsion | Hyperstimulation syndrome (OHSS) | Polycystic ovary syndrome (PCOS) |
|---|---|---|---|
| Symptoms | Acute pain, nausea, vomiting | Pain, nausea, vomiting | No pain (infertility, hirsutism) |
| Medical history | Often cysts/tumors | IVF procedure | Menstrual irregularities |
| Lesion | Unilateral (asymmetric) | Bilateral symmetric | Bilateral symmetric |
| Location of adnexa | Abnormal (anterior/posterior) | May prolapse into the iliac fossa | Normal |
| Position of the uterus | Deviated toward the side of torsion | Normal | Normal |
| Vascularity (CDM) | Variable (often absent) | Normal or increased | Normal |
Briefly: answers to topical questions
What acute surgical and gynecological conditions must ovarian torsion be differentiated from?
Ovarian torsion must be differentiated from the following acute surgical and gynecological pathologies:
- Acute appendicitis — especially with a pelvic location of the vermiform appendix.
- Renal colic.
- Ectopic pregnancy.
- Acute salpingo-oophoritis.
- Torsion or necrosis of a uterine fibroid.
- Intestinal obstruction.
- Perforated gastric ulcer.
What complications develop with prolonged torsion of the ovarian vascular pedicle?
Prolonged torsion of the ovarian vascular pedicle leads to complications associated with impaired blood circulation:
- Necrosis due to kinking of the nourishing vessels.
- Aseptic inflammation with subsequent spread to the pelvic peritoneum.
- Secondary infection.
- Peritonitis.
- Adhesion of the affected mass to adjacent organs.
What anatomical ligaments and structures form the ovarian vascular pedicle that undergoes torsion?
The ovarian vascular pedicle that undergoes torsion is formed by anatomical ligaments containing nourishing vessels, as well as adjacent structures.
- Suspensory ligament of ovary (lig. suspensorium ovarii / lig. infundibulopelvicum) — contains the ovarian artery and vein.
- Ovarian proper ligament (lig. ovarii proprium) — contains the ovarian branches of the uterine artery.
- Mesosalpinx is the mesentery of the uterine tube.
- Uterine tube — when stretched, it forms part of the surgical pedicle of an ovarian tumor.
Torsion leads to kinking of the blood vessels running within them.
What risk factors and background conditions contribute to the development of ovarian torsion?
Various background conditions and triggering factors contribute to the development of ovarian torsion.
- Benign tumors and cysts — especially formations with a diameter of 5 cm or more (dermoid cysts, corpus luteum cysts, serous cystadenomas).
- Ovarian hyperstimulation syndrome (OHSS).
- Characteristics of the mass — asymmetric shape, uneven density, and excessive mobility.
- Pregnancy and the postpartum period.
- Physical activity — sudden cessation of rotational body movements (dancing, gymnastics), physical exertion.
- Physiological changes — sharp changes in intra-abdominal pressure and increased intestinal peristalsis.
Specific symptoms of torsion are associated with rotation: on ultrasound and MRI, look for the twisted vascular pedicle — the "whirl sign" / "swirl sign".
Class and exam questions
Can torsion be completely ruled out if the ovary is of normal size?
With a high degree of probability, yes. Without enlargement of the organ to 7 cm or more, the diagnosis of torsion is considered unlikely.
Is blood flow on ultrasound always absent in ovarian torsion?
No, vascularity in torsion is variable. Although the absence of flow on color Doppler is very characteristic, its presence does not completely exclude the diagnosis.
What MRI findings indicate the presence of ovarian torsion?
Key MRI findings include the whirl sign (twisted vascular pedicle), the "beak sign" (wedge-shaped deformation of the mass), and the absence of contrast enhancement in the affected tissues.
What else to study on this topic
- Dermoid cysts of the ovary: MRI and CT features, complications (rupture, peritoneal gliomatosis)
- Ovarian hyperstimulation syndrome (OHSS): pathophysiology and imaging findings
- Ultrasound criteria for polycystic ovary syndrome (PCOS)
- Ovarian fibromas and thecomas: differential diagnosis of stromal tumors
- Vaginal cysts: topographic diagnosis relative to the pubic symphysis
- MRI evaluation of complications following mid-urethral sling placement and bulking agent injections
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Ovarian torsion" and 2,199 other pages on the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the section "Diagnostic Radiology of the Abdominal Organs"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.