A moderate amount of pressure may be needed to push behind the bowel.
The aorta should be imaged in B mode from the diaphragm to, and including,the iliac arteries.
- Begin with in a transverse plane in the epigastrum.
- Identify the spine with the aorta on the patients left and IVC on the patients right. Both immediately anterior to the spine.
- Slide inferiorly in the transverse plane observing the aorta carefully for changes in diameter.
- Approximately at umbilicus the aorta will bifurcate into the left and right iliac arteries.
- Maintain the same depth as you survey-slide down the aorta. This will allow you to easily appreciate any changes in diameter.
- When assessing the iliac artery origins, umbilcus may cause shadowing. Lift your probe and place afew cm below umbilicus and angle cranially.
- On challenging patients, use graduated pressure as the patient exhales, over afew respiratory cycles.
- To assess the most diaphragmatic aspect of the Aorta, using an over-hand probe grip can provide better pressure and accessibility if the patient has a large abdomen.
- From the transverse plane, rotate into longitudinal
- Fan to the patients right to identify the IVC. This is to ensure you are on the Aorta, and not a distended IVC.
ALL measurements should be outer wall to outer wall.
The maximal AP and Transverse Diameter are measured in the Proximal, Mid and Distal abdominal aorta.
If an aneurysm is identified ( >3cm in a male and >2.5cm in a female ) then the distance from the renal arteries should be measured . Supra or infra renal should be documented.
The maximal AP and Transverse diameters should be measured in the origin of the iliac arteries and if an aneurysm is seen then the scan should be extended to include the common , internal and external iliac arteries.
If the aneurysm extends into the bifurcation and includes one or both of the iliacs, this should be documented.
Colour doppler demonstrates the residual lumen and documents patency of the abdominal aorta.
On pulsed wave doppler, the normal proximal aorta will have a mixed, biphasic waveform. The distal aorta should have a triphasic waveform. This is not critical in the assessment for an AAA.
A “heel toe” movement to ensure an angle <60 degrees is used for accuracy in any velocity measurements.