An abdominal aortic aneurysm is a dangerous swelling of your largest blood vessel, the aorta. A screening ultrasound scan is offered to all men in their 65th year. Men over 65 can self-refer. The aim is to detect a possible aneurysm before it causes a problem, and either to monitor it closely, or to consider surgical treatment.
Follow this link for more info: http://www.nhs.uk/conditions/abdominal-aortic-aneurysm-screening/Pages/Introduction.aspx