An aneurysm is an abnormal dilation of a blood vessel, affected the whole or part of its circumference. An aortic aneurysm affects the largest blood vessels in the body which runs from the heart to the pelvis. If the aneurysm is in the chest, it is known as a thoracic aortic aneurysm, if it is in the abdomen it is and abdominal aortic aneurysm (Figure) and if it extends from the chest to the abdomen it is know as a thoracoabdominal aortic aneurysm.
Cause: The cause of aortic aneurysms is not known though there are several theories. Advancing age, male sex, smoking and a positive family history all increase the chances of a normal aorta becoming aneurysmal.
Complications: The main risk of an aortic aneurysm is the risk of rupture. Rupture is usually fatal. Small aneurysms (<5cm in diameter) rarely rupture and are usually monitored for growth using ultrasound from year to year. Once an aneurysm exceeds 5cm in diameter then treatment may be recommended.
Once an aneurysm reaches the threshold for intervention the shape and extend of the aneurysm will determine which treatment modality is required, open or endovascular repair (see Interventions).
CT scan reconstruction showing an abdominal aortic aneurysm (arrow).