Coloured 3D computed tomography (CT) scan of the heart (centre-left) and aorta (bodyIllustrations main artery, large red tube) of a patient who has had a stent (gold mesh) placed in an aortic aneurysm. A stent is a tube implanted into blood vessels to prevent narrowing and provide structural support, in this case to prevent the aneurysm from rupturing. An aneurysm is a bulging of a section of blood vessel which can occur when the blood vessel wall becomes weakened and thin. The exact cause is not fully known but risk factors include smoking, age, genetics and high blood pressure. Symptoms vary depending on where the aneurysm occurs, but generally include pain in the affected area. In some cases, aneurysms can rupture, which can lead to severe internal bleeding and death. Stents can avoid the need for more invasive surgical treatment to prevent this.