Coloured computed tomography (CT) angiogram scan of the abdomen of a 65 year old male patient with an aortic aneurysm (centre) above the renal arteries. The aorta is the body's main artery. An aneurysm is a dilation of the artery wall, and can be fatal if it ruptures. This aneurysm is a complication of aortoiliac occlusive disease, also known as Leriche Syndrome. Leriche Syndrome is caused by severe atherosclerosis, a condition in which an artery wall thickens as a result of accumulations (atheromas) of fatty materials such as cholesterol. It involves the blockage of the abdominal aorta below the renal arteries as it transitions into the common iliac arteries.