Aortic aneurysm repair. Coloured X-ray of a stent (grey/green) inserted into the aorta to repair an aneurysm, the ballooning of a weakened blood vessel wall. The aorta (main body artery) divides into the two iliac arteries (lower left), which each supply a leg. The wire mesh stent provides support for the walls of the arteries. Aneurysms are usually caused by blood vessel disease, most commonly atherosclerosis. This occurs when plaques of atheroma (a fatty substance) are deposited on the inside walls of arteries. Aneurysms may put pressure on surrounding organs and tissues, disrupting their function. They may also rupture, which may be swiftly fatal.