Aortic aneurysm near kidneys. 3D computed tomography (CT) angiogram of an aneurysm (swelling, pink, centre) in the aorta near the kidneys in a 67-year-old man. An aneurysm is a blood-filled dilation in a blood vessel wall. It is caused by a weakening of the vessel wall, which may be caused by hardening of the vessel (atherosclerosis), high blood pressure or injury. If left untreated an aneurysm can rupture, which is often fatal.