The natural history of abdominal aortic aneurysms (AAA) is that of slow expansion and rupture with devastating consequences.The risk of rupture is proportional to the size of the aneurysm and the rate of growth.  Differing rates of rupture for a given aneurysm size have been reported in the literature but the general consensus is that aneurysms greater than 5.0 cm in women and 5.5 to 6.0 cm in men carry a significantly increased risk of rupture and should be treated.  Furthermore, aneurysms that expand greater than 10 mm per year are also at significant risk of rupture and are considered for treatment even when less than 5.0 cm.