Thursday, March 29, 2018

False Perpetuations: Ovarian Torsion, Doppler Ultrasound, and CT

Ryan schwope ovarian torsion ax CT
ovarian torsoin US Ryan Schwope
Contrast-enhanced CT (top) and gray-scale US (bottom) in the same patient, both modalities demonstrating right ovarian torsion. Note the enlarged and heterogenous right ovary, peripheral follicles, and ascites

  • False Perpetuation: After a normal CT for lower abdominal or pelvic pain, an ultrasound with color Doppler is necessary to "rule out ovarian torsion"
  • Ovarian/adnexal torsion is caused by complete or partial rotation of the ovarian pedicle on its long axis. This results in lymphatic and venous congestion, inturn limiting arterial inflow
    • Torsion of both the ovary and fallopian tube occurs more often than that of either structure alone
    • Occurs more frequently on the right
  • Findings on Ultrasound
    • Enlarged ovary
    • Eccentric mass (usually a cyst) serving as a lead point
    • Round/'full' ovary with a central 'ground glass' appeaerance
    • Peripheral follicles
    • The presence of (or decrease in) arterial/venous flow predicts a better outcome
      • The absense of ovarian flow suggests necrosis
    • Even if there is ovarian flow on Doppler imaging, there can still be torsion
      • One study (J Ultrasound Med 2001; 20:1083-1089) evaulated the use of Doppler in pathologic proven cases of ovarian/adnexal torsion and found:
        • No arterial or venous flow in 40% of cases
        • No venous flow, decreased arterial flow in 7% cases
        • No arterial flow, decreased venous flow in 33% cases
        • Decreased arterial and venous flow in 13% cases
        • Normal arterial and venous flow in 7% cases
      • A meta-analysis (Eur J Pediatr Surg 2015; 25:82-86) looked at different modalities in diagnosing ovarian torsion in pediatric patients. Regarding morphologic and Doppler criteria on ultrasound for the diagnosis of ovarian torsion, this study found:
        • Morphologic features: 92% sensitive and 96% specific
          • Some of the morphologic features reviewed:
            • Enlarged heterogenous ovary (compared to contralateral normal ovary)
            • Ovarian volume 12x larger than contralateral volume, or 75 mL absolute ovarian volume
            • Ovarian diameter 2.3x larger than contralteral diameter
            • Multiple peripheral cortical follicles with transudative fluid
            • Whirlpool-sign
            • Cystic mass, particularly > 5cm in diameter
        • Doppler: 55% sensitive and 87% specific
  • Thus, the diagnosis of ovarian torsion is made or excluded based on grayscale appearance, not the Doppler findings
  • Regarding CT and ovarian torsion
    • One study (Abdom Imaging 2015; 40:3206-3213) retrospectively evaluated the utility of Doppler ultrasound in the assessment of ovarian torsion following a negative contrast-enhanced CT (the ultrasound and CT were performed within a 24 hour period) found:
      • Of the 48 cases with ovarian enlargement (defined as greater than 5 cm), 11 had torsion
      • Of the 235 cases without ovarian enlargment, 0 had torsion
      • Other CT findings assessed:
        • Presense of free fluid
        • Uterine deviation
        • Fallopian tube thickening
        • Smooth wall thickening of a cystic mass
        • Ovarian fat stranding
        • Twisted Pedicle
        • Abnormal ovarian enhancement
      • The most common ultrasound finding associated with ovarian torsion was ovarian enlargement (either due to the enlarged ovary itself or a mass functioning as a lead point)
      • A completely negative CT was never associated with a Doppler ultrasound suspicious for ovarian torsion (negative predictive value of 100%)
  • There is no utility in the addition of a Doppler Ultrasound (specifically for the evaluation of ovarian torsion) following a negative contrast-enhanced CT of the abdomen and pelvis
  • Ovarian size should be used as a dominant feature in the exclusion of ovarian torsion on both CT and US
*This blog was inspired by and based on a workshop given at the Society of Abdominal Radiology 2018 annual meeting by Dr. Maitray D. Patel of Mayo Clinic Arizona

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