Diagnostic Ultrasound - Abdomen and Pelvis
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Diagnostic Ultrasound - Abdomen and Pelvis

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Adnexal/Ovarian Torsion TERMINOLOGY Synonyms • Ovarian torsion ○ Adnexal torsion is more accurate term, as torsion usually also includes fallopian tube – Isolated fallopian tube torsion may also rarely occur Definitions • Rotation of ovary on its vascular pedicle resulting in venous congestion and ultimately infarction of ovary IMAGING General Features • Best diagnostic clue ○ Enlarged ovary, often echogenic, with prominent peripheral follicles and absent venous flow on endovaginal color Doppler sonography ○ Twisted vascular pedicle • Location ○ Torsed ovary/tube is often displaced from normal location – Midline, cephalad, anterior to uterine fundus, or in culde-sac • Size ○ Enlarged ovary: > 4 cm in longest dimension or > 20 cm³ in volume – > 10 cm³ in postmenopausal women ○ Torsed ovary averages 28x normal volume • Morphology ○ Swollen, rounded contour Ultrasonographic Findings • Grayscale ultrasound ○ Enlarged, heterogeneously echogenic ovarian stroma ○ Multiple small peripheral fluid-filled follicles displaced due to edematous stroma &/or mass ○ Follicle walls may become thickened and echogenic as torsion progresses ○ Ovarian cystic or solid mass ○ Ovary tends to be displaced midline, superior to uterus or down into cul-de-sac ○ Ovary is tender to touch by ultrasound probe ○ Pelvic free fluid; low-level echoes indicate hemoperitoneum ○ Twisted vascular pedicle (broad ligament, fallopian tube, ovarian vessels) – Sweep through pedicle with dynamic clip shows whirlpool sign – Target sign: Round hyperechoic structure, multiple hypoechoic concentric stripes – Beaked structure: Twisted fallopian tube – Heterogeneous tubular structure: Edematous fallopian tube ○ Isolated fallopian tube torsion: Often adnexal cyst separate from ovary, dilated tube with normal ovary • Pulsed Doppler ○ Flow pattern depends on degree of vascular obstruction and chronicity of torsion ○ Normal arterial and venous waveforms may be present, especially in acute torsion – May also be seen with incomplete (< 360°) twist ○ Venous flow affected 1st ○ Due to dual arterial blood supply to ovary, arterial flow may be preserved – Resistive indices may be elevated ○ Absent venous and arterial flow in late torsion/ovarian infarction • Color Doppler ○ Whirlpool sign: Coiled, twisted pedicle CT Findings • NECT ○ Ovarian hematoma/hematosalpinx best seen (> 50 HU) • CECT ○ Enlarged displaced ovary ○ Use multiplanar reformations to better see twisted pedicle – Most specific sign, but only seen in < 1/3 of cases ○ Deviation of uterus toward side of torsion ± displaced ovary towards midline ○ Hypodense edematous stroma with peripherally placed cysts ○ Heterogeneous, minimal, or absent enhancement indicates evolution from ischemia to infarction MR Findings • T1WI ○ Hypointense ovarian edema ○ Hyperintensity indicates hemorrhagic infarction or hemorrhagic cyst – Look for hyperintense rim typical of subacute hematoma ○ Hyperintense fallopian tube/vascular pedicle (hemorrhage) • T2WI ○ Hyperintense small peripheral cysts with background of increased ovarian signal intensity • T1WI C+ ○ Degree of enhancement variable depending on severity of ischemia and infarction ○ Best for twisted pedicle and evaluating for underlying mass Imaging Recommendations • Best imaging tool ○ Endovaginal US with both grayscale and color Doppler is best initial imaging examination – Reported accuracy of US varies among studies (23- 75%) ○ CT/MR more likely to show twisted pedicle DIFFERENTIAL DIAGNOSIS Hemorrhagic Corpus Luteum • Most common entity to be confused for torsion • Variable appearance of cyst in otherwise normal-appearing ovary ○ "Fishnet" or lace-like fibrinous strands ○ Retracting clot ○ Fluid-fluid level ○ Diffuse low-level echoes similar to endometrioma • Increased flow around cyst on color Doppler Diagnoses: Female Pelvis 857

Adnexal/Ovarian Torsion Diagnoses: Female Pelvis Pelvic Inflammatory Disease • Uniformly thickened and dilated fallopian tubes • Pyosalpinx ○ Contains low-level echoes or fluid-fluid level • ± enlarged ovaries secondary to oophoritis ○ Normal or increased flow pattern on color Doppler • ± tubo-ovarian abscess ○ Complex cystic/solid masses • "Indefinite uterus" sign ○ Obscuration of posterior margin of myometrium by inflammation Ectopic Pregnancy • Positive β-hCG • No evidence of intrauterine pregnancy on endovaginal sonography • Adnexal mass separate from ovary ○ Tubal ring with increased flow ("ring of fire") • Visualization of embryo or yolk sac within tubal gestational sac • Free fluid in pelvis and Morison pouch from hemoperitoneum PATHOLOGY General Features • Etiology ○ In adults, 50-90% have associated ovarian mass, usually benign – Large physiologic follicular cyst or corpus luteum cyst is most common – Dermoid, paraovarian cyst, and epithelial and stromal tumors can also serve as lead points for torsion ○ Infants and children rarely have associated mass – Hypermobility due to long mesosalpinx ○ Isolated tubal torsion may occur due to hydrosalpinx, hematosalpinx, tubal neoplasms, tubal ligation, tubal hypermotility, and hydatid of Morgagni Gross Pathologic & Surgical Features • Torsion of both ovary and fallopian tube most commonly found at surgery ○ Isolated torsed fallopian tube possible • Ovarian torsion occurs around suspensory ligament of ovary ○ Posterior fold of broad ligament that contains ovarian vessels • Twist ranges 180-720° • Sequential venous, lymphatic, and arterial obstruction • Earliest pathologic changes include edema and microscopic hemorrhage within ovary ○ Begins centrally • Prominent fluid-filled follicles displaced peripherally by central edema • Late findings include hemorrhagic infarction ○ Cystic spaces filled with blood and associated hemoperitoneum • Calcified mass in chronic cases CLINICAL ISSUES Presentation • Most common signs/symptoms ○ Severe unremitting acute pelvic pain is most common symptom – Pain may be intermittent torsion/detorsion ○ Adnexal mass may or may not be palpable ○ Vomiting is common ○ Fever if ovary is infarcted Demographics • Epidemiology ○ 2-3% of all gynecologic emergencies ○ Most common in first 3 decades ○ More common during pregnancy – Usually before 20 weeks – As uterus enlarges, ovaries are pushed out of pelvis increasing risk of torsion ○ Increased risk in women undergoing ovarian stimulation ○ Increased risk in women with prior pelvic or abdominal surgery Natural History & Prognosis • Spontaneous detorsion can recur ○ Massive ovarian edema felt to result from episodes of intermittent torsion with detorsion – Usually long history of intermittent pain • Presence of venous flow indicates viable ovary • If no flow seen, ovary is infarcted Treatment • Surgical untwisting in noninfarcted adnexa either with laparoscopy or open surgery ○ Preservation of ovary is possible if normal blood flow is restored after detorsing ovary • Careful examination and removal of any mass serving as lead point • Salpingo-oophorectomy in infarcted ovary DIAGNOSTIC CHECKLIST Consider • Ectopic pregnancy in pregnant patient Image Interpretation Pearls • Absent venous flow in enlarged echogenic ovary with prominent peripheral follicles is earliest reliable sign • Presence of normal blood flow does not exclude torsion • Always look for underlying mass SELECTED REFERENCES 1. Lourenco AP et al: Ovarian and tubal torsion: imaging findings on US, CT, and MRI. Emerg Radiol. 21(2):179-87, 2014 2. Narayanan S et al: Fallopian tube torsion in the pediatric age group: radiologic evaluation. J Ultrasound Med. 33(9):1697-704, 2014 3. Sasaki KJ et al: Adnexal torsion: review of the literature. J Minim Invasive Gynecol. 21(2):196-202, 2014 4. Duigenan S et al: Ovarian torsion: diagnostic features on CT and MRI with pathologic correlation. AJR Am J Roentgenol. 198(2):W122-31, 2012 5. Sibal M: Follicular ring sign: a simple sonographic sign for early diagnosis of ovarian torsion. J Ultrasound Med. 31(11):1803-9, 2012 6. Wilkinson C et al: Adnexal torsion -- a multimodality imaging review. Clin Radiol. 67(5):476-83, 2012 858

Adnexal/Ovarian Torsion<br />

TERMINOLOGY<br />

Synonyms<br />

• Ovarian torsion<br />

○ Adnexal torsion is more accurate term, as torsion usually<br />

also includes fallopian tube<br />

– Isolated fallopian tube torsion may also rarely occur<br />

Definitions<br />

• Rotation of ovary on its vascular pedicle resulting in venous<br />

congestion <strong>and</strong> ultimately infarction of ovary<br />

IMAGING<br />

General Features<br />

• Best diagnostic clue<br />

○ Enlarged ovary, often echogenic, with prominent<br />

peripheral follicles <strong>and</strong> absent venous flow on<br />

endovaginal color Doppler sonography<br />

○ Twisted vascular pedicle<br />

• Location<br />

○ Torsed ovary/tube is often displaced from normal<br />

location<br />

– Midline, cephalad, anterior to uterine fundus, or in culde-sac<br />

• Size<br />

○ Enlarged ovary: > 4 cm in longest dimension or > 20 cm³<br />

in volume<br />

– > 10 cm³ in postmenopausal women<br />

○ Torsed ovary averages 28x normal volume<br />

• Morphology<br />

○ Swollen, rounded contour<br />

Ultrasonographic Findings<br />

• Grayscale ultrasound<br />

○ Enlarged, heterogeneously echogenic ovarian stroma<br />

○ Multiple small peripheral fluid-filled follicles displaced<br />

due to edematous stroma &/or mass<br />

○ Follicle walls may become thickened <strong>and</strong> echogenic as<br />

torsion progresses<br />

○ Ovarian cystic or solid mass<br />

○ Ovary tends to be displaced midline, superior to uterus<br />

or down into cul-de-sac<br />

○ Ovary is tender to touch by ultrasound probe<br />

○ Pelvic free fluid; low-level echoes indicate<br />

hemoperitoneum<br />

○ Twisted vascular pedicle (broad ligament, fallopian tube,<br />

ovarian vessels)<br />

– Sweep through pedicle with dynamic clip shows<br />

whirlpool sign<br />

– Target sign: Round hyperechoic structure, multiple<br />

hypoechoic concentric stripes<br />

– Beaked structure: Twisted fallopian tube<br />

– Heterogeneous tubular structure: Edematous<br />

fallopian tube<br />

○ Isolated fallopian tube torsion: Often adnexal cyst<br />

separate from ovary, dilated tube with normal ovary<br />

• Pulsed Doppler<br />

○ Flow pattern depends on degree of vascular obstruction<br />

<strong>and</strong> chronicity of torsion<br />

○ Normal arterial <strong>and</strong> venous waveforms may be present,<br />

especially in acute torsion<br />

– May also be seen with incomplete (< 360°) twist<br />

○ Venous flow affected 1st<br />

○ Due to dual arterial blood supply to ovary, arterial flow<br />

may be preserved<br />

– Resistive indices may be elevated<br />

○ Absent venous <strong>and</strong> arterial flow in late torsion/ovarian<br />

infarction<br />

• Color Doppler<br />

○ Whirlpool sign: Coiled, twisted pedicle<br />

CT Findings<br />

• NECT<br />

○ Ovarian hematoma/hematosalpinx best seen (> 50 HU)<br />

• CECT<br />

○ Enlarged displaced ovary<br />

○ Use multiplanar reformations to better see twisted<br />

pedicle<br />

– Most specific sign, but only seen in < 1/3 of cases<br />

○ Deviation of uterus toward side of torsion ± displaced<br />

ovary towards midline<br />

○ Hypodense edematous stroma with peripherally placed<br />

cysts<br />

○ Heterogeneous, minimal, or absent enhancement<br />

indicates evolution from ischemia to infarction<br />

MR Findings<br />

• T1WI<br />

○ Hypointense ovarian edema<br />

○ Hyperintensity indicates hemorrhagic infarction or<br />

hemorrhagic cyst<br />

– Look for hyperintense rim typical of subacute<br />

hematoma<br />

○ Hyperintense fallopian tube/vascular pedicle<br />

(hemorrhage)<br />

• T2WI<br />

○ Hyperintense small peripheral cysts with background of<br />

increased ovarian signal intensity<br />

• T1WI C+<br />

○ Degree of enhancement variable depending on severity<br />

of ischemia <strong>and</strong> infarction<br />

○ Best for twisted pedicle <strong>and</strong> evaluating for underlying<br />

mass<br />

Imaging Recommendations<br />

• Best imaging tool<br />

○ Endovaginal US with both grayscale <strong>and</strong> color Doppler is<br />

best initial imaging examination<br />

– Reported accuracy of US varies among studies (23-<br />

75%)<br />

○ CT/MR more likely to show twisted pedicle<br />

DIFFERENTIAL DIAGNOSIS<br />

Hemorrhagic Corpus Luteum<br />

• Most common entity to be confused for torsion<br />

• Variable appearance of cyst in otherwise normal-appearing<br />

ovary<br />

○ "Fishnet" or lace-like fibrinous str<strong>and</strong>s<br />

○ Retracting clot<br />

○ Fluid-fluid level<br />

○ Diffuse low-level echoes similar to endometrioma<br />

• Increased flow around cyst on color Doppler<br />

Diagnoses: Female <strong>Pelvis</strong><br />

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