Aneurysmal disease is the dilation of the arterial walls caused by a variety of factors. Arteriosclerosis is usually the most common cause, secondary to smoking, hypertension and hypercholesterolaemia; certain genetic abnormalities of the arterial walls can also contribute to their progressive deformation.

It can affect any artery in the body, although the abdominal aorta, the thoracic aorta and the popliteal artery (in the legs) are the most commonly affected.

When an artery becomes dilated, it can rupture and cause a haemorrhage that can be fatal. In the case of the popliteal artery, the complication is thrombosis and, as a result, blockage of the artery.