This chapter should be cited as follows:
Sibal M, Gundabattula SR, Glob Libr Women's Med
ISSN: 1756-2228; DOI 10.3843/GLOWM.419713

The Continuous Textbook of Women’s Medicine Series – Gynecology Module

Volume 10

Ultrasound in gynecology

Volume Editors: Professor Antonia Testa, Agostino Gemelli University Hospital, Rome, Italy
Professor Simona Maria Fragomeni, Agostino Gemelli University Hospital, Rome, Italy

Chapter

Ultrasound Diagnosis of Adnexal Torsion

First published: December 2025

AUTHOR(S)

Mala Sibal, DGO, DNB

Department of Fetal Medicine and OBGyn Ultrasound, Manipal Hospital, Bangalore, India

Sirisha R Gundabattula, MD

Department of Gynaecology, Fernandez Hospital, Hyderabad, India

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INTRODUCTION

Torsion is defined as the twisting of a bodily organ or part on its own axis.¹ Torsion of an ovary refers to twisting of the ovary on its ligamentous supports causing compromised blood flow to the ovary. Often the Fallopian tube twists along with the ovary and this is referred to as adnexal torsion. Other adnexal structures, such as a paraovarian or paratubal cysts, may also undergo torsion.

Adnexal torsion is noted in about 2–3% of women presenting with acute pelvic pain.²^,³ In a 10-year review, ovarian torsion accounted for 2.7% of emergency surgeries in women and was the fifth most common diagnosis following ectopic pregnancy, ruptured corpus luteal cyst, pelvic inflammatory disease and appendicitis.⁴ Ovarian hyperstimulation may be complicated by torsion in 8–12% of cases.⁵ Adnexal torsion is most common in women of reproductive age group but no age is exempt.

Adnexal torsion involves the tube and ovary in about 67% of cases.³ Isolated tubal torsion is less common and seen typically when the Fallopian tube is dilated (hydrosalpinx). Prompt diagnosis is important to preserve the function of the ovary and/or Fallopian tube. However, this can be challenging at times as symptoms are non-specific leading to diagnostic delay.

RISK FACTORS AND PATHOPHYSIOLOGY

The presence of a benign ovarian lesion is the single greatest risk factor for adnexal torsion (Table 1) with dermoid cyst and serous cystadenoma being the most commonly found pathologies. Corpus luteal cysts account for most cases of torsion in the first trimester of pregnancy.

Risk factors for adnexal torsion.²^,³^,⁵

Ovarian torsion	Tubal torsion
Ovarian mass (> 85%), particularly if ovary ≥ 5 cm Previous adnexal torsion (11–19%), especially if it was torsion of normal adnexa Pregnancy Ovarian hyperstimulation Polycystic ovary Tubal sterilization	Tubal pathology Hydrosalpinx Hematosalpinx Neoplasm Ectopic pregnancy Paraovarian/paratubal cyst Ovarian mass (predisposes to ovarian and tubal torsion)

Torsion is more common on the right side probably because of the presence of the sigmoid colon on the left and the longer utero-ovarian ligament on the right.²^,⁵^,⁶ Ovaries fixed in the pelvis are less likely to tort as seen in endometrioma, tubo-ovarian abscess and malignancy. In postmenopausal women, ovarian torsion is uncommon; however, when it does occur, the rate of malignancy may be as high as 3–20%, compared with an overall malignancy rate of less than 3% in torsed ovaries.²^,⁷^,⁸

As the ovary twists on its ligamentous supports, its vascular supply becomes compromised. The severity of the vascular impairment depends on the number of twists, the tightness of the twists and duration since the twist. This can result in partial or complete vascular obstruction, which some refer to as partial or complete torsion, respectively. Following the twist, the lymphatic and venous channels are compromised first, because they have thinner walls and are more compressible. This causes vascular congestion and results in stromal edema. With ongoing torsion, this edema compromises arterial flow in the arterioles and capillaries resulting in ischemia, hemorrhage and necrosis.² As a result, the torsed ovaries often appear enlarged and bluish-black at surgery.

CLINICAL FEATURES AND NATURAL HISTORY

Most patients with adnexal torsion are symptomatic. Asymptomatic presentation might signal either necrotic adnexa or non-compromised twisted ovary. The common symptoms and signs include:²^,³^,⁵

Acute pelvic pain (44–97%)
Nausea and vomiting (47–70%)
Fever (2–20%)
Abdominal tenderness (70%)
Palpable mass (20–47%)
Rebound tenderness (adnexal necrosis)

The pain is unilateral and is often triggered by exercise or a sudden movement that alters intra-abdominal pressure, such as straining during bowel movements, lifting heavy objects or performing yoga. It may radiate to the flank or back and can be constant or intermittent.

The potential adverse outcomes of a missed diagnosis include:⁵

Autoamputation/atrophy over time of the ovary
Pelvic adhesions
Persistent pelvic pain with repeat hospital visits
Tubal infertility (if the remaining ovary is functional)
Hemorrhage and peritonitis

DIAGNOSIS

The diagnosis of torsion is primarily based on clinical suspicion supported by sonographic findings. However, symptoms are non-specific and ultrasound examination is key to early diagnosis. Unfortunately, ultrasound is considered to have limited specificity and sensitivity of 79% and 76%, respectively;⁹ and laparoscopy is still commonly resorted to for diagnosis, when ultrasound findings or imaging are negative or inconclusive.

For ultrasound evaluation in clinically suspected torsion, a transabdominal scan is performed first, followed by a transvaginal scan. Most of the sonographic features of torsion described below are best visualized on transvaginal or transrectal scans. However, the transabdominal approach can be useful for identifying structures such as a twisted pedicle, as the full bladder displaces non-pelvic structures superiorly, providing a panoramic and unobstructed view of the pelvic anatomy.

Commonly seen non-specific ultrasound findings

Enlarged ovary – torsion is more common in ovaries that are enlarged with a functional cyst, a benign neoplastic mass or hyperstimulation. Congestion and edema of the ovarian stroma secondary to torsion also contribute to the increased size.
Hemorrhagic cysts – hemorrhage within the cyst could be because of a physiological hemorrhagic corpus luteal cyst or due to hemorrhage into the cyst secondary to torsion.
Abnormal position – the torsed ovary may be displaced from its usual position and, consequently, its location may not correlate with the reported site of pain. It may be seen on the opposite side, anterior to the uterus or impacted in the pouch of Douglas.
Free fluid – this is frequently seen in women of reproductive age even in the absence of torsion. In cases of torsion, free fluid is almost always present. Therefore, the absence of free fluid should prompt reconsideration of the diagnosis, as it may not be a case of torsion.
Tenderness – the torsed organs are frequently tender to touch but probe tenderness may not be evident after analgesic administration.

Specific ultrasound findings

Twisted ovarian pedicle with the whirlpool sign – the twisted pedicle appears as an extraovarian heterogeneous mass which is elongated and tubular on long section and appears as a circumscribed mass on transverse section. It appears hyperechoic with multiple concentric hypoechoic stripes or shows hypoechoic beads within (engorged vessels) and often has a bright echogenic center, appearing as the ‘target sign’.
The whirlpool sign is a spiral pattern produced when the probe is moved gently along the long axis of the pedicle on grayscale and Doppler. In order to elicit the sign, a heterogeneous mass around the organ suspected to have torsed should be looked for, followed by rotation of the probe to visualize the cross-section of the pedicle, i.e. ‘target sign’, and then angulation along the pedicle to elicit the whirlpool sign and possibly count the number of twists.
The pedicle can mimic other pelvic structures such as the Fallopian tubes and intestinal loops but the whirlpool sign of the twisted pedicle is a very specific feature of ovarian torsion.
Follicular ring sign – this is the presence of prominent thick (1–2 mm) hyperechoic margins of antral follicles in the torsed ovary. It results from increased hydrostatic pressure of the capillaries around the antral follicles following obstruction of venous flow with continuing arterial flow and leads to edema and hemorrhage in the follicular walls. This is an early feature of torsion, which is easy to detect, the only prerequisite being the visualization of antral follicles. As torsion progresses, the edema and hemorrhage spread to the rest of the ovarian stroma, making the follicular ring sign less distinct.
Ovarian stromal edema – this is typically seen as bulky afollicular stroma with or without peripherally displaced follicles. The stroma appears heterogeneous and hyperechoic due to congestion and hemorrhage. It may appear as a solid mass on transabdominal scan where the peripheral antral follicles may not be well seen. It has reduced utility when ovarian tissue is minimal or not seen and is not a feature of non-ovarian torsion. Sometimes, afollicular ovarian tissue is misconstrued as edema.
Absent Doppler flow – in early torsion, blood flow may be normal followed by loss of venous and then arterial flow. Absent flow is a late feature and difficult to assess when tissue is limited as in a torsed paraovarian cyst or hydrosalpinx. Normal Doppler flow does not exclude the diagnosis of torsion.

The ultrasound findings of adnexal torsion are summarized in Table 2 and depicted in Figures 1 and 2. An enlarged ovary, hemorrhagic cysts, abnormal position, free fluid and tenderness are commonly seen. The specific findings which can be used in diagnosis are: ovarian stromal edema, whirlpool sign of the twisted pedicle, absent Doppler flow and the follicular ring sign. The contralateral non-torsed ovary provides a convenient control to elicit the sonographic findings.

Summary of ultrasound features of adnexal torsion.²^,³^,⁵^,¹⁰^,¹¹^,¹²^,¹³

Ultrasound feature	Advantage	Limitation
Enlarged ovary can be the cause or effect of torsion	Common finding	Non-specific feature
Hemorrhagic cyst: cysts if present are typically hemorrhagic and thick walled	Ovarian and non-ovarian torsion	Non-specific feature
Abnormal position: unusual location of the ovary such as contralateral, anterior to uterus or in pouch of Douglas		Non-specific feature Location may vary depending on extent of bladder filling
Free fluid: small amount of fluid usually seen		Non-specific feature
Probe tenderness: torsed organs typically tender		May not be elicited after analgesia Non-specific feature
Twisted pedicle: extraovarian heterogeneous mass showing the ‘target sign’		Mimics Fallopian tube and intestine
Whirlpool sign (91%): spiral pattern produced when the probe is moved gently along the long axis of the pedicle on grayscale and Doppler	Specific feature Ovarian and non-ovarian torsion	Expertise needed to elicit the sign
Follicular ring sign (49%): prominent 1–2 mm thick hyperechoic margins of antral follicles due to perifollicular edema and hemorrhage	Early feature Highly specific feature in the presence of antral follicles Limited skills	Antral follicles not seen because of large masses or after menopause Not seen in non-ovarian torsion
Ovarian edema (79%): seen as bulky afollicular stroma with or without peripherally displaced follicles; may appear as a solid mass on transabdominal scan	Specific feature	Late feature Cannot be seen when ovarian tissue is minimal or because of large masses or dermoid Not seen in non-ovarian torsion
Absent Doppler flow (52%): following a twist, first venous and then arterial flow is lost; in early torsion, flow may be normal	Specific feature	Late feature False positive if Doppler settings are not optimized Difficult to assess when tissue is limited

Non-specific ultrasound findings of ovarian torsion: (a) enlarged ovary secondary to a dermoid cyst; (b) enlarged right ovary as a result of torsion-induced edema with normal left ovary; (c) hemorrhagic cyst; (d) extraovarian pedicle; (e) torsed left ovary displaced to the right side; (f) free fluid.

Specific ultrasound findings of ovarian torsion: (a) twisted pedicle with whirlpool sign; (b) follicular ring sign in right ovary and normal antral follicles in left ovary; (c) ovarian stromal edema; (d) absent Doppler flow in torsed left ovary with normal flow in right ovary.

Of the four specific features of torsion, the whirlpool sign is present from the onset in all types of adnexal torsion. As lymphatic and venous flow become compromised, the follicular ring sign is seen as an early feature of ovarian congestion. Ovarian stromal edema with or without peripherally displaced follicles is seen later as ovarian congestion and edema progress. Absent flow is a late feature of torsion when arterial flow is compromised resulting in ischemia and necrosis. This is depicted in Figure 3 and Videoclip 1.

Timeline of events in adnexal torsion.

Specific ultrasound findings of ovarian torsion in order of appearance.

Special situations

Torsion with necrosis and gangrene

When torsion with necrosis and gangrene occur, symptoms may paradoxically lessen. On ultrasound, there is often complete loss of normal ovarian architecture with markedly heterogeneous ovarian tissue. No flow is typically seen on Doppler. In some cases, the shape of the ovary may change transiently with probe pressure, and gelatinous necrotic tissue may demonstrate a characteristic 'jiggling' motion when intermittent pressure is applied.

Torsion of the Fallopian tube

Usually, the tube torts along with the ovary, and is visualized as a thickened segment of the Fallopian tube close to the twisted pedicle. This is typically difficult to identify on ultrasound particularly because the tube does not have any specific feature to help identify it.

Torsion of a hydrosalpinx can occur in isolation and is usually identified by the whirlpool sign. Other sonographic features of torsion that may be seen are thickened walls, turbid hemorrhagic intraluminal fluid and absent flow within the walls (though this can be difficult to assess). The dilated tube is often located medial to a normal ipsilateral ovary, tapering at either end in a configuration known as the 'beak' sign.²^,¹⁴

Torsion of paraovarian cyst

Paraovarian and paratubal cysts may also undergo torsion, which is usually isolated but may involve the ovary or Fallopian tube. Diagnosis of paraovarian cyst torsion is made using the whirlpool sign. Other features that may be seen are thickened walls, turbid intraluminal fluid and absence of flow in the cyst walls (difficult to assess). If the ovary is not involved, the antral follicles on that side do not show the follicular ring sign.

Figure 4 presents a simple flowchart for the sonographic assessment of torsion. In a pilot study conducted in our center (unpubl. data), follicular ring sign was seen in 50 of 74 (68%) cases of confirmed ovarian torsion while, in the remainder, the antral follicles could not be visualized.

Simple flow diagram of ultrasound diagnosis of adnexal torsion.

Computed tomography and magnetic resonance imaging

In women with acute pelvic pain, ultrasound is the initial imaging modality of choice, especially if gynecological etiology is suspected. Imaging with computed tomography (CT) and magnetic resonance imaging (MRI) may be helpful if ultrasound is inconclusive in centers with limited expertise. The accuracy of CT scan for torsion is as low as 42% because the pedicle twist can be difficult to visualize on CT images. MRI is often unavailable in the acute setting and is primarily used in atypical cases to clarify equivocal findings seen with other modalities, aid anatomic localization and/or characterize lead masses if there is a concern for malignancy.²^,⁵^,¹⁵

Definitive preoperative confirmation of torsion is vital because a false-negative report can lead to loss of tubo-ovarian function while a false-positive diagnosis can result in complications from a surgical exploration, particularly in pregnant women or those with endometriosis or previous abdominal surgery.¹⁶

DIFFERENTIAL DIAGNOSIS

The clinical differential diagnosis of adnexal torsion includes all major causes of acute pelvic pain (Table 3).

Differential diagnosis of adnexal torsion²^,³^,⁵

Clinical differential	Ultrasound differential
Pregnancy-related Ectopic pregnancy Miscarriage Adnexal pathology Pelvic inflammatory disease Ruptured ovarian cyst Endometrioma with hemorrhage Uterine cause Adenomyosis Fibroid with torsion, degeneration Obstructive anomaly with hematometrocolpos Non-gynecological cause Appendicitis Ureteric colic	Enlarged ovary Ovarian mass Ovarian hyperstimulation Ovarian displacement Adnexal mass Ovarian edema Massive ovarian edema Peripherally placed follicles Polycystic ovary Extraovarian pedicle Fallopian tube Bowel loop

Clinical differential

Ultrasound differential

Pregnancy-related

Ectopic pregnancy
Miscarriage

Adnexal pathology

Pelvic inflammatory disease
Ruptured ovarian cyst
Endometrioma with hemorrhage

Uterine cause

Adenomyosis
Fibroid with torsion, degeneration
Obstructive anomaly with hematometrocolpos

Non-gynecological cause

Appendicitis
Ureteric colic

Enlarged ovary

Ovarian mass
Ovarian hyperstimulation

Ovarian displacement

Adnexal mass

Ovarian edema

Massive ovarian edema

Peripherally placed follicles

Polycystic ovary

Extraovarian pedicle

Fallopian tube
Bowel loop

MANAGEMENT

Fear of thromboembolic complications and the misconception that bluish-black discoloration signified irreversible gangrene were unfounded myths that historically led to unnecessary oophorectomies. In current practice, once torsion is diagnosed, laparoscopic detorsion is the mainstay of treatment.²^,⁵^,¹⁷

Although some suggest that irreversible ovarian damage occurs if there is a delay in detorsion of ≥ 72 hours, the appearance of the ovary at surgery is not a reliable indicator of ovarian viability, and preservation of function has been reported in > 90% of cases after detorsion. Therefore, a torsed ovary must not be removed unless a severely necrotic ovary falls apart or there is a suspicion of malignancy or the woman is postmenopausal.

Conservative management of torsion via transabdominal or transvaginal ultrasound-guided cyst aspiration is an alternative in patients with simple anechoic cysts with anesthesia-related risks or with physiological cysts such as in pregnancy.¹⁸ Drainage of the cyst fluid may reduce the pressure in the adnexa and lead to spontaneous detorsion, failing which surgical management is recommended.

Postoperative follow-up

An ultrasound examination may be performed 4–6 weeks after the untwisting procedure, to document the preservation of the ovarian parenchyma, by assessing ovarian size, vascularization and follicular development, particularly in patients with no flow on Doppler.

PRACTICE RECOMMENDATIONS

Ultrasound is the imaging modality of choice for making a diagnosis in clinically suspected adnexal torsion.
Clinical symptoms are non-specific, the most common being unilateral acute pelvic pain, which may be intermittent.
Non-specific ultrasound features that are commonly seen include enlarged ovary, hemorrhagic cysts, abnormal position of the ovary and free fluid.
The specific ultrasound features of torsion are as follows:
- Whirlpool sign of the twisted pedicle is a useful sign, which can be seen from the outset in both ovarian and non-ovarian torsion. However, eliciting this sign requires considerable expertise.
- Follicular ring sign is a simple, early and specific feature of ovarian torsion, its limitation being lack of utility in non-ovarian torsion and ovarian torsion in which antral follicles cannot be visualized.
- Edematous ovarian stroma with or without peripherally placed follicles is a late feature and is of limited use when ovarian tissue is not visualized or is minimal.
- Absence of Doppler flow is a late feature and the presence of flow does not rule out torsion. Another pitfall associated with this feature is the possibility of a false-positive diagnosis if Doppler settings are not appropriate.
Management of torsion is by prompt surgical intervention (laparoscopy) to confirm the diagnosis, untwisting the torsed organ and excision of any lesion, if safe and feasible. The ovary should be left in situ even if it appears dusky unless the patient is postmenopausal, the mass is necrotic and friable or there is a concern of malignancy.

CONFLICTS OF INTEREST

The author(s) of this chapter declare that they have no interests that conflict with the contents of the chapter.

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REFERENCES

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