Imaging

Struma Ovarii

Preliminary Diagnosis: Struma ovarii

I. What imaging technique is first-line for this diagnosis?

  • Ultrasound (US) of the pelvis with transabdominal and endovaginal imaging for evaluation of the ovaries.

II. Describe the advantages and disadvantages of this technique for diagnosis of struma ovarii.

Advantages

  • Allows for evaluation of the ovaries, adnexa, and uterus.

  • Relatively quick examination which does not utilize ionizing radiation.

  • Useful in determining characteristics of ovarian lesions.

  • Can allow for assessment of vascular flow to ovarian lesions.

  • Cost-effective imaging modality.

  • If normal-appearing ovaries are seen, a diagnosis of struma ovarii can be excluded.

Disadvantages

  • Very operator-dependent, and relies heavily on the skill of the technologist or physician performing the exam.

  • Can be significantly degraded by patient body habitus and bowel gas content.

  • Endovaginal ultrasound, while more sensitive, is uncomfortable to some patients.

III. What are the contraindications for the first-line imaging technique?

  • There are no significant contraindications to transabdominal US examination of the pelvis.

  • Endovaginal US is much more sensitive, but may be declined by a subset of patients.

IV. What alternative imaging techniques are available?

  • Magnetic resonance imaging with intravenous gadolinium contrast.

  • Computed tomography (CT) with intravenous contrast.

  • Iodine-123 nuclear scan.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of struma ovarii.

Magnetic resonance imaging (MRI) with contrast

Advantages

  • Allows for high-resolution evaluation of the ovaries and pelvic structures.

  • Does not use ionizing radiation.

Disadvantages

  • Expensive

  • Time consuming

  • Requires significant patient cooperation to minimize motion artifact

CT with contrast

Advantages

  • Quick imaging exam which requires less patient cooperation than MRI.

  • Cost-effective.

Disadvantages

  • Utilizes ionizing radiation, which should be minimized for patients in reproductive age and children.

Iodine-123 nuclear scan

Advantages

  • Iodine-123 will be taken up by any functioning thyroid tissue, and is diagnostic of struma ovarii if seen in the adnexal region.

  • Can be done with Spect-CT imaging, allowing for CT and nuclear evaluation in the same examination.

Disadvantages

  • Lengthy examination.

  • Significant radiation dose that requires extensive patient preparation, post-imaging instructions, and occasionally patient isolation.

VI. What are the contraindications for the alternative imaging techniques?

MRI with contrast

  • Patients with embedded metallic devices not made of titanium such as cardiac pacers, stents, and other non-MR approved metallic devices may not enter the magnet for imaging.

  • Patients with GFR <30 cannot receive gadolinium intravenous contrast.

CT with contrast

  • Contraindicated in pregnancy, especially 1st and 2nd trimester.

  • Intravenous contrast should not be administered in patients with renal insufficiency, creatinine>1.6 mg/dL

  • Allergy to iodinated contrast media requires premedication per department protocol or in severe cases should not be given.

Iodine-123

  • Contraindicated in pregnant patients or patients who plan on becoming pregnant within 6 months.

  • Patients on thyroid replacement therapy will need to discontinue medication for 3-4 days prior to examination.

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