On chest x-ray, what is an aortic knob?

What does it mean when my x-ray result says prominent aortic knob? Thanks! More power!

Submitted by Joseph from Philippines on 04/27/2014

The aortic knob on a chest x-ray (CXR) represents part of the thoracic aorta (the very large blood vessel that connects the heart and supplies blood to rest of the body) called the aortic arch.

From your description, the doctor who interprets the CXR thinks that this part of the blood vessel (the aortic arch) could be a bit big (or prominent). CXR is a very good and useful tool in looking at the structures in the chest and provides a wealth of information. However, it also provides only an estimate to the size of the structures such as the thoracic aorta and aortic arch.

Certain past medical history, such as poorly controlled high blood pressure, can be a risk factor of increasing the size of the thoracic aorta. If there is a concern, you should discuss the report with your physician who ordered the test to see if there is a need to look into this further, e.g. by other imaging modality such as CT or MR that can accurately measure the size of the aorta.