An Aneurysm is a dilation of the vessel wall, generally of the abdomen. For example, if the abdominal aorta dilates in excess of 3mm, it’s considered an aneurysm. In rare cases aneurysms can be innate, but usually they are caused by arteriosclerosis in middle age. Aneurysms generally don’t cause any symptoms; therefore, preventive check-ups are recommended from the age of 50.