Ultrasound Quiz 3: All About Aortas

Question 1:

What structure is identified by the arrow?

Excellent! You were able to Identify the aorta which is non-compressible, has a thick echogenic (white) wall, and that it is anterior to the spine.

The arrow is pointing to the aorta.
Orient yourself!
In the far field, we can see a thick echogenic (white) line, with a big black shadow underneath it. This is the spine.

At the start at the scan, we can see 2 anechoic (black) spaces just anterior to the spine. These are the IVC and the Aorta. In order to help us identify which is which, we follow a few basic principles:
The aorta is non-compressible, it has a thick echogenic (white) wall, and it is found immediately anterior to the spine.

The IVC on the other hand is easily compressible, is tear-drop shaped, it does not usually have a clearly defined thick echogenic (white) wall. It is however also found anterior to the spine somewhat.

So based on these principles, we can ascertain that the anechoic (black) structure on screen left is the IVC since it is compressible and we cannot see any echogenic wall.
On screen right, you can see a round structure that isn't easily compressible with a thick echogenic (white) wall. This must be the aorta. Also, near the end of the scan, you can see the bifurcation of the aorta. This is super important, because when scanning the aorta, we need to start from the xiphoid process all the way down until we see the bifurcation of the aorta in order to rule out Abdominal Aortic Aneurysm.

Question 2:

A 60 year old male wit ha 2 pack/day smoking history presents to the ER with back pain. What do you notice on this US?

Great job! You didn't fall for the trap - always remember to measure the diameter from outer wall to outer wall!

This is a big aortic aneurysm of 6cm.
Remember to use the ladder on the right to measure the diameter of the aorta.

It's extremely important to measure the diameter of the aorta from outer wall to outer wall. This is because a blood clot could make the aorta seem smaller than it truly is, just like it is in this scan.
Remember - just because there's a blood clot in the aorta, doesn't mean the aneurysm ruptured! We can't identify that from ultrasound - just that there is an enlarged aorta.

Question 3:

A resident does a standard ultrasound on a patient with suspected AAA. She is surprised to see a structure that looks like smoke in the aorta, so they call you for a consult. You explain to them:

The patient was smoking so much that the smoke could no longer dissolve in the blood. The contrast is due to the interaction between RBCs and plasma proteins in low shear conditions. The aorta ruptured and the patient is about to go in shock. The patient has a very high fever and their blood is heating up as a result, producing this contrast. This is an IGG mediated reaction to an exogenous protein found in the blood. THE AORTA IS ON FIRE

Yes you're right! The aorta's not on fire, it's just an interaction between the RBCs and plasma proteins. Read more about it here: https://pubmed.ncbi.nlm.nih.gov/1452941/

So this is an interesting phenomenon found because of an interaction between RBCs and plasma proteins in low shear conditions. If you want to learn more about this, check out this article! https://pubmed.ncbi.nlm.nih.gov/1452941/

Remember, you cannot tell if an aorta ruptured or not from an ultrasound.