A 70 year old man presenting with abdominal pain has a mass in abdomen. Angiography reveals aneurysm of aoa. What is the MOST likely cause of aoic aneurysm?
Atherosclerosis is the most common cause of aoic aneurysm. Infrarenal abdominal aoa is most frequently affected by the atherosclerotic process and is the most common site of aneurysm formation. Abdominal aoa is more prone to develop aneurysm because it is less elastic, resulting from less elastin and more collagen, and it has higher pulsatile stress compared with ascending aoa. Media of infrarenal aoa in humans has no vaso vasorum, so inner media receive nutrition by diffusion from aoic lumen. Intimal thickening by atherosclerosis disturbs nutrition and hence wall nutrition. Thoracic aoic aneurysms greater than 60mm in diameter and abdominal aoic aneurysm greater than 50mm are prone to rupture. Ref: Diagnosis and Treatment of Aoic Diseases edited by Christoph A. Nienaber, page 58.
Trauma
Atherosclerosis
Syphilis
Congenital