Ultrasonography of the abdominal aorta
In this video, we'll show you how to perform an ultrasound scan of the abdominal aorta.
The most common reason to perform a point-of-care scan of the abdominal aorta
is to check for an aneurysm.
We'll talk about that a little later, but first we'll go over the basics of how to perform a scan, and some relevant anatomy.
The abdominal aorta is retroperitoneal and closely adjacent to the inferior vena cava.
We will be scanning the aorta in the short axis, otherwise known as the transverse plane.
We can use a curvilinear or phased array probe for these scans.
Short-axis view
Place the probe just under the xiphoid process, with the probe indicator pointing to the patient's right side.
Pushing the probe down firmly can improve the image by displacing any overlying abdominal gas.
You can now clearly make out two anechoic structures, lying just anterior to the hyperechoic vertebral body and its large acoustic shadow.
To the left of the image, just to the right of the patient's midline,
is the inferior vena cava, which we'll refer to as the IVC from now on.
To the right of the image, just to the left of the patient's midline,
you can see the abdominal aorta.
The IVC has a thinner wall than the aorta and can usually be compressed quite easily with the probe.
In contrast, the aorta is thick-walled and almost impossible to compress, remaining circular
under the probe. It also pulsates much more noticeably than the IVC.
Let's now take a look at the branches of the abdominal aorta.
We will scan the abdominal aorta and its branches from proximal to distal.
As the probe is moved distally, major arteries can be seen branching off the aorta.
First is the celiac trunk, which splits after a short distance into three branches.
The shape of the trunk's division in this view is sometimes called the "seagull sign",
because it looks a little like a silhouette of a seagull's wings.
Two of the branches are visible here: the common hepatic artery running right and the
splenic artery running left.
The celiac trunk's third major branch, the left gastric artery, is not visible in this
short axis view, because it initially runs proximally.
Directly below the celiac trunk is the superior mesenteric artery, which runs parallel to
the aorta distally. You can see it here in transverse section, crossing the left renal
vein and surrounded by a hyperechoic layer of fatty tissue.
Next, the left and right renal arteries can be seen branching from the aorta.
Finally, roughly at the level of the umbilicus, the aorta bifurcates into the left and right common iliac arteries.
To screen for an aneurysm, you need to visualize the abdominal aorta from the hiatus
all the way down to the bifurcation.
The aorta should normally be anechoic throughout its course.
An aortic diameter greater than 3 cm indicates the presence of an aneurysm.
To measure the aortic diameter, first freeze the image at the point where the aorta looks widest.
Then, measure from the outer border of the wall on one side to the outer border on the opposite side.
It's important not to measure only the lumen, because plaques and thrombi can make it appear falsely narrow.
Okay, now that you have an overview of aorta ultrasound skills, check out the POCUS article on AMBOSS.