An aortic aneurysm (say "a-OR-tik AN-yuh-rih-zum") is a bulge in a section of the aorta, the body's main artery. The aorta carries oxygen-rich blood from the heart to the rest of the body. Because the section with the aneurysm is overstretched and weak, it can burst. If the aorta bursts, it can cause serious bleeding that can quickly lead to death.

Aneurysms can form in any section of the aorta.

• They are most common in the belly area. This type is called an abdominal aortic aneurysm.
• They can also happen in the upper body. This type is called a thoracic aortic aneurysm. These are much less common than abdominal aortic aneurysms.

A pseudoaneurysm happens when a bulge occurs but doesn't affect all three layers of tissue in the wall of the aorta. This type of aneurysm might be caused by an injury.