Imaging

Renal Artery Stenosis

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

  • Inexpensive screening examination that is well-tolerated and widely available.

  • Peak systolic velocities correlate with the degree of stenosis.

  • Color Doppler may demonstrate turbulent flow.

  • Tardus-parvus waveform and acceleration times are indirect signs of stenosis.

Disadvantages

  • May not provide the anatomic detail required for treatment planning.

  • Results may be dependent on operator expertise.

  • May not be possible to visualize the entire length of the renal arteries.

  • 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?

  • CT angiography

  • MR angiography

  • Catheter angiography

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing renal artery stenosis.

CT angiography

Advantages

  • Improved anatomic detail to localize and demonstrate the extent of disease as compared to ultrasound.

  • Provides detailed evaluation of surrounding viscera and accurately detects small accessory renal arteries.

  • 3D and multiplanar reformatted images may aide treatment planning.

Disadvantages

  • Risk of contrast-induced nephropathy with exposure to contrast material.

  • Exposure to ionizing radiation.

  • May be difficult to interpret in heavily calcified arteries.

MR angiography

Advantages

  • Improved anatomic detail to localize and demonstrate the extent of disease as compared to ultrasound.

  • Accurately detects hemodynamically significant renal artery stenosis.

  • 3D and multiplanar reformatted images may aide treatment planning.

Disadvantages

  • Expensive.

  • Time consuming.

  • Requires significant patient cooperation to minimize motion artifact.

  • Long examination times may not be well-tolerated by claustrophobic patients.

Catheter angiography

Advantages

  • Traditional gold-standard for diagnosis.

  • Evaluates intrarenal vascular abnormalities in addition to abnormalities of the renal arteries and aorta.

  • Translesional pressure gradients help determine if a stenosis is hemodynamically significant.

  • Allows for treatment at the time of diagnostic examination.

Disadvantages

  • Risk of contrast-induced nephropathy with exposure to iodinated contrast material.

  • Risk of access site and catheter associated injury.

  • Interobserver variability in the visual estimation of the degree of stenosis.

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

CT angiography

  • Renal failure due to the risk of contrast induced nephropathy.

  • Pregnancy.

  • Contrast allergy may be a relative contraindication.

MR angiography

  • Certain implanted devices, such as pacemakers and aneurysm clips, may not be MRI compatible.

  • Renal failure due to the risk of nephrogenic systemic fibrosis.

  • Pregnancy in the first trimester may be a relative contraindication.

Catheter angiography

  • Renal failure due to the risk of contrast induced nephropathy (may be a relative contraindication due to the possibility of using CO2 contrast).

  • Pregnancy.

  • Contrast allergy may be a relative contraindication.

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