Preliminary Diagnosis: Superior vena cava syndrome

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

  • CT with IV contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of superior vena cava syndrome.

Advantages
  • Will establish the level and extent of obstruction
  • Can guide therapeutic options by mapping collaterals and patent vasculature
  • Can determine if an obstructing lesion is intrinsic or extrinsic to the superior vena cava (SVC) and evaluate other critical structures
Disadvantages
  • Exposure to ionizing radiation
  • Risk of contrast-induced nephropathy

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

  • Renal failure
  • Pregnancy

IV. What alternative imaging techniques are available?

  • MRI
  • Ultrasound
  • Angiography
  • Radionuclide imaging with Tc-99m pertechnetate
  • Plain-film radiography

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of superior vena cava syndrome.

MRI
Advantages
  • Demonstrates non-opacification of the SVC, similar to CT
  • MR venography can map out the extent and degree of venous obstruction and collateral circulation, which may aid in operative planning
  • Can evaluate causes of obstruction external to the SVC
  • May be performed without intravenous contrast
Disadvantages
  • Expensive
  • Long examination times require patient cooperation
  • Certain implanted metallic devices are non-compliant
  • Risk of nephrogenic systemic fibrosis in renal failure patients
Ultrasound
Advantages
  • Cost-effective noninvasive examination
  • May demonstrate dilated SVC and distended collateral vessels
  • Can show absent or sluggish blood flow
Disadvantages
  • Operator-dependent
  • Does not evaluate entire SVC
Angiography
Advantages
  • Conventional venography is the gold standard for diagnosing abnormalities of the SVC, demonstrating lack of contrast flow through the SVC
  • May be used in treatment planning for endovascular procedures
Disadvantages
  • Angiography may not reveal the primary pathology that results in extrinsic obstruction
  • It is an invasive procedure with risk of infection, bleeding, and vessel injury
  • Risk of contrast-induced nephropathy in patients with renal failure
Radionuclide imaging with Tc-99m pertechnetate
Advantages
  • The radionuclide injected in the brachial vein can demonstrate obstruction of flow to the right heart and enlarged collateral veins
Disadvantages
  • Limited evaluation of the underlying pathology
Plain-film radiography
Advantages
  • Simple examination to demonstrate widening of the superior mediastinum due to mediastinal mass or dilated SVC
  • Cost-effective screening modality with minimal radiation exposure
Disadvantages
  • Findings are nonspecific
  • Normal chest radiography does not exclude SVC obstruction

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

MRI
  • Pacemakers, non-compatible metallic implants, and aneurysm clips
  • Renal failure if contrast is administered due to the risk of nephrogenic systemic fibrosis
  • Pregnancy during the first trimester may be a relative contraindication
Ultrasound
  • No significant contraindications
Angiography
  • Renal failure due to risk of contrast-induced nephropathy
  • Contrast allergy may be a relative contraindication
Radionuclide imaging with Tc-99m pertechnetate
  • Pregnancy and breast feeding
Plain-film radiography
  • No significant contraindications exist. Some institutions may require consent in pregnant patients.