Preliminary Diagnosis: Pheochromocytoma

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

MRI abdomen with IV contrast

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

Advantages
  • This technique may identify extra-adrenal lesions, which account for 10% of pheochromocytomas.
  • Does not use ionizing radiation.
Disadvantages
  • This technique is expensive.
  • Requires patient cooperation.
  • Longer imaging time.

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

  • There are contraindications for patients with non-MRI approved metallic devices.
  • Gadolinium is contraindicated in patients with a GRF <30-40 mL/min/1.73m2, due to the risk of nephrogenic systemic fibrosis.

IV. What alternative imaging techniques are available?

  • CT abdomen and pelvis with contrast.
  • Nuclear medicine scan (MIBG).

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

CT abdomen and pelvis with contrast
Advantages
  • CT is equally sensitive to MRI, and may be used as first line imaging.
  • May identify extra-adrenal lesions, which account for 10% of pheochromocytomas.
  • This is a quick imaging procedure which requires minimal patient cooperation and is less susceptible to motion artifact.
Disadvantages
  • Hypertensive crisis has been described with use of older, ionic contrast agents. However, hypertensive crisis is rare or nonexistent with use of modern non-ionic contrast agents and routine pre-medication with alpha and beta blockade is not recommended.
  • Pheochromocytoma is not distinguished from other adrenal lesions by imaging appearance alone. History and lab values are necessary for diagnosis.
  • Ionizing radiation exposure.
  • Administration of iodinated contrast may result in worsening renal function (contrast nephropathy) in patients with renal insufficiency. Contrast dose should be reduced or withheld in these patients.
Nuclear medicine scan (MIBG)
Advantages
  • Whole body imaging detects extra-adrenal and metastatic disease.
  • More specific than MRI or CT.
Disadvantages
  • Imaging may take 2-3 days.
  • Less sensitive than MRI or CT, and you may see positive findings in cases of neuroblastoma, carcinoid tumor, medullary thyroid carcinoma, and ganglioneuroma.

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

CT abdomen and pelvis with contrast
  • Contraindicated in pregnant women, especially in the first two trimesters.
  • Relative contraindication in patients with contrast allergy.
  • Relative contraindication in patients with renal failure.
Nuclear medicine scan (MIBG)
  • Contraindicated during pregnancy.
  • Contraindicated while breastfeeding.

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