Aortic aneurysm. Coloured computed tomography (CT) scan of two axial sections through the chest of a 46-year-old man with an aortic aneurysm (artery ballooning). The severely enlarged aneurysm is the pale blue area at the centre of each scan. The front of the body is at the top. The aorta is the main artery passing blood from the heart to the lower body. The artery wall may be weakened by disease, such as atherosclerosis. Without surgery, an aortic aneurysm may rupture with fatal consequences.