ABSTRACT
The etiology of the artherosclerotic abdominal aortic aneurysm is still controversial. Different theories developed in independent ways. Probably therefore thedifferent concepts developed independently, and were not considered together to explain the different aspects of the etiology of this peculiar vascular pathology. Recently a tendency appeared to try to put together the different theories since it became clear that etiology of the aneurysm could not be explained by a single ideia. The biomecanical is based upon the fact that the infra-renal abdominal aorta has a tapered fashion, is more rigid than the thoracic aorta and is more prone to suffer the influence of the reflection waves caused by the branches. It has also fewer elastic lamelae in its wall and fewer vessels arising from its vasa vasorum. It seems possible that the artherosclerotic disease contributes to impar the nutrition of the vessel wall. Although the growing rate of an aneurysm is determined by Laplace's law, the ultimate stability of the aneurysm can beexplained by recruitment of collagen fibers, by the progressive rigidity of the wall and by the modification of the geometry of the wall. Mural trombi and smooth muscle fibers do add very little to the wall strength. The theory of the influence of metals in the development of the aneurysm is based upon the clinical and experimental evidences of a participation of the copper metabolism upon the development of aneurysms of the aorta. The genetic theory is based upon the fact that there is probably a familiar tendency for the appearance by an aortic aneurysms. The proteolytic theory explains the aneurysm by an imbalance between proteolysis and anti-proteolysis although the findings of diminishment of elastin and collagen in theaortic wall were not considered to be primary. The most important risc factors such as hipertension and cigarette smoking do probably act as mechanical and metabolic factors. Is is very likely that thete abdominal aortic aneurysm should be explained by an association of a proteolytic and anti-proteolytic imbalance, a genetic predisposition, a structural pesisposition and hemodynamic factors related to the aorto-iliac geometry. HYpertension yn and cigarette smoking doact as worsening factors