Preliminary Diagnosis: Renal Artery Stenosis
I. What imaging technique is first-line for this diagnosis?
Ultrasound
II. Describe the advantages and disadvantages of this technique for diagnosing renal artery stenosis.
Advantages
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Inexpensive screening examination that is well-tolerated and widely available.
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Peak systolic velocities correlate with the degree of stenosis.
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Color Doppler may demonstrate turbulent flow.
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Tardus-parvus waveform and acceleration times are indirect signs of stenosis.
Disadvantages
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May not provide the anatomic detail required for treatment planning.
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Results may be dependent on operator expertise.
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May not be possible to visualize the entire length of the renal arteries.
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Duplicated renal arteries may be missed.
III. What are the contraindications for the first-line imaging technique?
No absolute contraindications exist.
IV. What alternative imaging techniques are available?
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CT angiography
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MR angiography
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Catheter angiography
V. Describe the advantages and disadvantages of the alternative techniques for diagnosing renal artery stenosis.
CT angiography
Advantages
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Improved anatomic detail to localize and demonstrate the extent of disease as compared to ultrasound.
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Provides detailed evaluation of surrounding viscera and accurately detects small accessory renal arteries.
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3D and multiplanar reformatted images may aide treatment planning.
Disadvantages
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Risk of contrast-induced nephropathy with exposure to contrast material.
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Exposure to ionizing radiation.
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May be difficult to interpret in heavily calcified arteries.
MR angiography
Advantages
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Improved anatomic detail to localize and demonstrate the extent of disease as compared to ultrasound.
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Accurately detects hemodynamically significant renal artery stenosis.
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3D and multiplanar reformatted images may aide treatment planning.
Disadvantages
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Expensive.
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Time consuming.
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Requires significant patient cooperation to minimize motion artifact.
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Long examination times may not be well-tolerated by claustrophobic patients.
Catheter angiography
Advantages
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Traditional gold-standard for diagnosis.
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Evaluates intrarenal vascular abnormalities in addition to abnormalities of the renal arteries and aorta.
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Translesional pressure gradients help determine if a stenosis is hemodynamically significant.
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Allows for treatment at the time of diagnostic examination.
Disadvantages
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Risk of contrast-induced nephropathy with exposure to iodinated contrast material.
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Risk of access site and catheter associated injury.
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Interobserver variability in the visual estimation of the degree of stenosis.
VI. What are the contraindications for the alternative imaging techniques?
CT angiography
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Renal failure due to the risk of contrast induced nephropathy.
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Pregnancy.
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Contrast allergy may be a relative contraindication.
MR angiography
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Certain implanted devices, such as pacemakers and aneurysm clips, may not be MRI compatible.
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Renal failure due to the risk of nephrogenic systemic fibrosis.
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Pregnancy in the first trimester may be a relative contraindication.
Catheter angiography
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Renal failure due to the risk of contrast induced nephropathy (may be a relative contraindication due to the possibility of using CO2 contrast).
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Pregnancy.
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Contrast allergy may be a relative contraindication.
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