Ovarian torsion

Ovarian torsion is a difficult diagnosis to make.

A definitive diagnosis of ovarian torsion can only be made by direct visualization of a rotated ovary at the time of surgical evaluation, by either laparoscopy or laparotomy.

Timely laparoscopic evaluation with the aim of preservation of ovarian function and prevention of potentially serious complications is the cornerstone of treatment.

Epidemiology

• Ovarian torsion is an uncommon but important condition
• The majority of cases occur in young women of reproductive age of around 25 – 35 years

Pathophysiology

Ovarian torsion refers to the complete or partial rotation of the ovary on its ligamentous supports, often resulting in ischemia.

Torsion results in compression of the ovarian vasculature, initially reducing lymphatic and venous outflow. Lymphatic and venous outflow are compromised first due the thinner, more compressible walls of those vessels.

Arterial perfusion with blocked venous outflow results in edema and ovarian enlargement, further worsening compression of the vasculature, eventually leading to impaired arterial inflow with resulting ischemia, and necrosis of the ovary.

The mobility of the left ovary tends to be limited somewhat by the sigmoid colon, hence about two thirds of adnexal torsions are right sided.

Aetiology

Torsion of a normal ovary/ adnexa is uncommon, and it is usually the result of an underlying risk factor.

Recognised risk factors include:

1. Adnexal mass lesions (approximately 50-80 % of cases).
   • Ovarian tumours:
     • Benign (such as dermoid cysts)
     • Malignant
       • Malignant tumours are less likely to undergo torsion due to the presence of cancerous adhesions that fix the ovary to the surrounding structures.
   • Ovarian physiologic cysts.
   • Polycystic ovaries
   • Paraovarian cysts
2. Developmental abnormalities leading to hypermobility of the ovary    
3. Pregnancy:
   • Enlarged corpus luteum cysts and the laxity of supporting structures. risk of torsion is greatest in the first trimester and decreases thereafter as the corpus luteum regresses in the second trimester.
   • The rate of torsion increases by 5 times during pregnancy
4. Assisted conception:
   • The induction of ovulation during infertility treatment can lead to ovarian hyperstimulation syndrome and expansion of the ovarian volume thus predisposing to torsion
5. Previous pelvic surgery:
6. Prior ovarian torsion
7. Strenuous activity

Clinical features

Diagnosis of ovarian torsion can be extremely difficult.

The classic presentation of ovarian torsion involves:

• Sudden onset of severe, unilateral, lower abdominal / pelvic pain (90% of cases)
• Nausea and vomiting
• A woman of reproductive age  
• The presence of a risk factor such as an ovarian mass or prior ovarian torsion

Important points of Examination:

1. Observations:
   • Necrosis of the ovary may lead to late systemic findings such as pyrexia, tachycardia and hypotension.
2. Abdominal examination
   • Unilateral tenderness
   • Signs of frank peritonism indicate possible infarction / peritonitis

Investigations

A definitive diagnosis of ovarian torsion can only be made by direct visualisation of a rotated ovary at the time of surgical evaluation, by either laparoscopy or laparotomy.

Blood tests

1. FBE
2. CRP:
   • A significantly elevated level suggests:
     • A severe complication such as necrosis / secondary infection 
     • A possible alternate diagnosis, such as appendicitis.
3. U&Es/ glucose:
4. Beta HCG:
   Beta-HCG should be done in all cases to exclude:
   • A concomitant pregnancy
   • A ruptured ectopic pregnancy (important differential diagnosis)

Ultrasound

• Currently considered the first line imaging modality for the evaluation of ovarian torsion.
• It may make the diagnosis; however, it cannot definitely exclude it. 
• The preferred method is a trans-vaginal ultrasound.

Ultrasound features of ovarian torsion include:

1. Ovarian tenderness to transducer pressure.
2. An enlarged hypo or hyperechoic ovary:
   • The main feature of torsion is ovarian enlargement.
3. A long-standing infarcted ovary may have a more complex appearance with cystic or hemorrhagic degeneration
4. Abnormally placed ovary: may be located more towards the midline in torsion
5. A “string of pearls” sign – ovarian follicles are seen to be congregated around the periphery of the ovary
6. Free pelvic fluid (> 80 % of cases)
7. An underlying ovarian lesion:

On Doppler ultrasound:

1. Blood flow abnormalities:

• Little or no intra-ovarian venous flow (common)
• Absent arterial flow (less common, but poor prognostic sign)
• Absent or reversed diastolic flow

Note that the absence of ovarian Doppler flow is highly specific for torsion, however normal Doppler flow does not completely exclude torsion.

2. A “whirlpool sign” of a twisted vascular pedicle:

• It is most commonly described with regard to bowel rotating around its mesentery, with mesenteric vessels creating the whirls but is also seen in cases of ovarian torsion.
• It appears as a twisted vascular pedicle.

CT Scan

If ultrasound examination is inconclusive, then a CT scan with contrast, of the abdomen and pelvis, can be done if clinical suspicion remains high.

A CT scan with contrast can essentially rule out an ovarian torsion if normal ovary/adnexa is seen.

It is also useful in situations where US is not available in an appropriately timely manner. 

Highly suggestive signs of ovarian torsion include:

1. Reduced or absent ovarian enhancement with contrast
2. Peripherally displaced follicles
3. Enlarged ovary with a follicular ovarian stroma
4. A thickened fallopian tube with target/beak-like appearance.

Features that are not specific but may suggest torsion include:

1. Periovarian fat stranding
2. Adnexal wall thickening
3. Free pelvic fluid
4. Ovarian mass or enlargement
5. Ovarian displacement towards the uterus or uterine deviation towards the torted ovary.

Laparoscopy / laparotomy

Ultimately if all imaging remains inconclusive, and yet clinical suspicion nonetheless remains high, laparoscopy (or laparotomy) remains the final option for definitive diagnosis.   

Management

Ovarian torsion is a gynecological emergency requiring urgent surgery to prevent ovarian necrosis. 

1. Analgesia:
   • Pain is usually moderate to severe and titrated IV opioids will be required.
2. Fluid resuscitation
3. Antibiotics: may be required for late presentations complicated by infection.
4. Surgery:
   • Minimising ischemic time is vital, however, the time to necrosis in ovarian torsion remains unclear based on the current literature.
   • In general terms, ovarian salvage rates decrease with increasing ischemic times, and so once the diagnosis is made (or strongly suspected), operation becomes urgent.
   • While there is no absolute cutoff to ensure viability, some studies have indicated that the best outcomes are achieved if the ovary is detorted within 8 hours, however viability will depend on the degree of ischemia as well as the time passed.

The important point is surgical intervention as soon as the diagnosis is made or strongly suspected.

Complications

• Ovarian loss with necrosis

A necrotic ovary can become infected and cause:

• A local abscess
• Generalized peritonitis.
• Hemorrhage

In the longer term:

• Impaired fertility:
  • The necrotic tissue will involute over time, but there may be secondary pelvic adhesion formation, which can result in chronic pelvic pain or infertility.
  • Unrecognized tubal torsion will result in loss of tubal function, and likely hydrosalpinx or necrosis with eventual resorption of the damaged tissue.

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References

FOAMed

• Ovarian Torsion. CORE EM
• Fox SM. Ovarian Torsion. Pediatric EM Morsels

Publications

• Bridwell RE, Koyfman A, Long B. High risk and low prevalence diseases: Ovarian torsion. Am J Emerg Med. 2022 Jun;56:145-150.