Renal Artery Stenosis Protocol
- A regular renal protocol is always included in a RAS study. This page illustrates the vascular portion only. Scanning Duration: 40 minutes.
Aorta Mid Sag At Renals
- Obtain the aorta peak systolic velocity (PSV) at the level of the renal arteries. Right lateral approach is preferred to show the renal artery origin ("banana peel" view).
- Doppler angle ≤60 degrees. Color image: One optimized image with renal artery origin, if possible.
Doppler image: Sample the center of the vessel with the angle parallel to the vessel walls.
Measurement: Take PSV only.
Aorta Mid Sag (Right Lateral approach)
Right MRA (Prox-Dist)
- Spend time to survey vascular anatomy, and to find an optimal window either anteriorly or laterally based on your patient.
- If you have the option, use the lateral approach scanning sagittal to the aorta and kidney. This will help you to check for accessory renal arteries or early MRA branches. Color image/cine: Show the entire MRA from the aorta origin to the kidney, proving it is the MRA.
Right MRA Prox-Dist (Right Lateral and Anterior approaches)
Right MRA Prox/Mid/Dist
- Doppler all accessory renal arteries or proximal branches when they are present, using an angle ≤60 degrees.
- Normal PSV ≤180 cm/s, or a value less than 3.5 times the aorta PSV.
- The normal velocity should taper gradually from proximal to distal MRA. One study has found that an abrupt decrease in velocity from mid/proximal to distal MRA by a factor of more than 2.7 indicates a renal artery stenosis. Doppler image: Sample the proximal, mid, and distal segments.
Measurement: Take PSV (EDV not necessary) for each MRA segment.
Right MRA Mid
Right MRV
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Color image: One optimized image.
Doppler image: Sample the mid renal vein to show patency.
Right MRV
Right Segmental Upper/Mid/Lower
- For the patient's comfort, avoid scanning the intrarenals with the aid of deep respiration. First find your window, then tell the patient to suspend breathing or hold in very small breaths.
- Sample the segmental arteries at the junction between renal hilum and cortex, using a Doppler angle ≤20 degrees.
- Increase the sweep speed and decrease the Doppler scale to zoom in the waveform.
- Normal RI <0.7, acceleration index >300 cm/s2, acceleration time <70 ms (0.07 s). Doppler image: Sample the upper, mid, and lower pole segmental arteries.
Measurements: Place four calipers (see above diagram) used to take PSV, EDV, RI, acceleration index, and acceleration time.
Right Segmental Upper, Mid, and Lower
(Repeat the protocol for the left side)
Worksheet
- Print the worksheet containing measurements.