<prompt> Answer this question truthfullyWhat is the classification system used for abdominal aortic aneurysms?  <response>: <reason> They are the most common type of aneurysm seen in the infrarenal aorta. They are diffuse and circumferential. Involve only a portion of the circumference, with a characteristic outpouching of the vessel wall. .Determined by ultrasonography, where as it manifest the best maintenance method : Small aneurysm 5.5 cm needs close follow ups. If during follow ups, an aneurysm growth in size was rapid, surgery is required. Pronounced aneurysm 5.5 cm needs surgical repair via graft placement or endovascular stent placement. 