The aorta is divided anatomically into the Thoracic Aorta and the Abdominal Aorta. Each can be further subdivided into three sections.
THORACIC AORTA: spans from the T3-T12 spinal levels, above the diaphragm.
- Ascending Aorta: from the sternal angle to T4/T5.
- Aortic Arch: starts at T4/T5, reaches T3, ends at T4.
- The aortic arch has 3 main branches visible on ultrasound from the suprasternal notch: the brachiocephalic artery, the left common carotid artery, and the left subclavian artery.
- Descending Thoracic Aorta: T4-T12, where it becomes the abdominal aorta after passing through the aortic hiatus in the diaphragm.
ABDOMINAL AORTA: spans from the T12 to L4 spinal levels, below the diaphragm. The proximal and mid abdominal aorta are collectively known as the suprarenal abdominal aorta. The distal abdominal aorta is considered the infrarenal abdominal aorta.
- Proximal Abdominal Aorta: spans from the diaphragm, celiac trunk to the superior mesenteric artery (SMA).
- Mid Abdominal Aorta: spans roughly from the SMA to the level of the renal arteries.
- Distal Abdominal Aorta: spans from the level of the renal arteries to the iliac bifurcation.
For ultrasound, visualizing the abdominal aorta is much more feasible than visualizing the complete thoracic aorta since much of the thoracic aorta is surrounding by lung/air (which ultrasound can’t penetrate through).
Most of this post will go over how to visualize the abdominal aorta all the way to the iliac bifurcation. However, there are parts of the thoracic aorta you can see using the suprasternal view described later on in the post.
