Preliminary Diagnosis: Superior vena cava syndrome
I. What imaging technique is first-line for this diagnosis
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CT with IV contrast
II. Describe the advantages and disadvantages of this technique for diagnosis of superior vena cava syndrome.
Advantages
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Will establish the level and extent of obstruction
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Can guide therapeutic options by mapping collaterals and patent vasculature
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Can determine if an obstructing lesion is intrinsic or extrinsic to the superior vena cava (SVC) and evaluate other critical structures
Disadvantages
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Exposure to ionizing radiation
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Risk of contrast-induced nephropathy
III. What are the contraindications for the first-line imaging technique?
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Renal failure
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Pregnancy
IV. What alternative imaging techniques are available?
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MRI
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Ultrasound
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Angiography
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Radionuclide imaging with Tc-99m pertechnetate
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Plain-film radiography
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of superior vena cava syndrome.
MRI
Advantages
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Demonstrates non-opacification of the SVC, similar to CT
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MR venography can map out the extent and degree of venous obstruction and collateral circulation, which may aid in operative planning
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Can evaluate causes of obstruction external to the SVC
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May be performed without intravenous contrast
Disadvantages
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Expensive
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Long examination times require patient cooperation
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Certain implanted metallic devices are non-compliant
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Risk of nephrogenic systemic fibrosis in renal failure patients
Ultrasound
Advantages
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Cost-effective noninvasive examination
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May demonstrate dilated SVC and distended collateral vessels
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Can show absent or sluggish blood flow
Disadvantages
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Operator-dependent
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Does not evaluate entire SVC
Angiography
Advantages
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Conventional venography is the gold standard for diagnosing abnormalities of the SVC, demonstrating lack of contrast flow through the SVC
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May be used in treatment planning for endovascular procedures
Disadvantages
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Angiography may not reveal the primary pathology that results in extrinsic obstruction
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It is an invasive procedure with risk of infection, bleeding, and vessel injury
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Risk of contrast-induced nephropathy in patients with renal failure
Radionuclide imaging with Tc-99m pertechnetate
Advantages
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The radionuclide injected in the brachial vein can demonstrate obstruction of flow to the right heart and enlarged collateral veins
Disadvantages
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Limited evaluation of the underlying pathology
Plain-film radiography
Advantages
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Simple examination to demonstrate widening of the superior mediastinum due to mediastinal mass or dilated SVC
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Cost-effective screening modality with minimal radiation exposure
Disadvantages
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Findings are nonspecific
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Normal chest radiography does not exclude SVC obstruction
VI. What are the contraindications for the alternative imaging techniques?
MRI
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Pacemakers, non-compatible metallic implants, and aneurysm clips
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Renal failure if contrast is administered due to the risk of nephrogenic systemic fibrosis
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Pregnancy during the first trimester may be a relative contraindication
Ultrasound
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No significant contraindications
Angiography
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Renal failure due to risk of contrast-induced nephropathy
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Contrast allergy may be a relative contraindication
Radionuclide imaging with Tc-99m pertechnetate
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Pregnancy and breast feeding
Plain-film radiography
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No significant contraindications exist. Some institutions may require consent in pregnant patients.
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