 Abdominal aortic aneurysms are commonly divided according to their size and symptomatology.An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm), or more than 50% of normal diameter that of a healthy individual of the same sex and age.If the outer diameter exceeds 5.5 cm, the aneurysm is considered to be large.