An aortic aneurysm is a bulge that occurs in the wall of the body's main artery, called the aorta, which carries blood from the heart to the body. Aortic aneurysms can occur anywhere in the aorta and may be tube-shaped or round. They include abdominal aortic aneurysms. Typically, there are no symptoms except when the aneurysm dissects or ruptures, which causes sudden, severe pain in the abdomen and lower back. Known causes include trauma, infection, and inflammatory disorders. Aortic aneurysms can rupture or dissect and cause life-threatening bleeding.