<prompt> All of the following are true about aoic aneurysm except:-Saccular aneurysm involves whole circumferenceTrue aneurysm involves all 3 layersAtherosclerosis is the commonest causeFalse aneurysm is not covered by all 3 layers  <response>: Degenerative aneurysms caused by atherosclerosis are MC AAA 90 . True all three layers of vessel are involved, false do not have all three layers of vessel Infected mycotic aneurysm are false aneurysm Dissecting aneurysm dissection with aneurysmal dilatation of false lumen Fusiform symmetrical enlargement involving whole circumference of aery Saccular affect only pa of the aerial circumference have higher risk of rupture 