Stent in carotid aneurysm. 3D computed tomography (CT) angiogram of the abdomen and pelvic region of a 59-year-old patient, showing stents (white mesh, centre) in place in the abdominal aorta and iliac arteries to treat an extra-aortic aneurysm. An aneurysm occurs when an artery wall weakens and swells like a balloon. If it bursts, an aneurysm can cause severe internal haemorrhage. Stents are mesh tubes inserted into the artery to strengthen and hold open the affected area to prevent rupture.