Doctors are not sure what causes most abdominal aortic aneurysms to form.
Weakened Aortic Wall Stretches Over Time
A leading theory is that there is degradation of certain structural elements of the aortic wall that cause it to weaken. The pressure of blood pumping through the aorta causes the weakened wall to stretch out and enlarge over time.
Process Linked to Atherosclerosis
Some researchers believe this process is linked to atherosclerosis -- hardening of the arteries -- or the risk factors that lead to atherosclerosis, including high blood pressure and smoking.