What is the treatment for an abdominal aortic aneurysm?

Depends: That depends on the size; if it is large or growing in size over 1cm a year, then it requires surgical repair. This can be done either through open surgery or more commonly these days, through endovascular repair through a small cut in your groin. You should see a vascular surgeon soon.

Size: Abdominal aneurysms should be treated surgically if greater than or equal to 6 cm (sometimes 5.5 cm depending on the age and risks), if symptomatic or if it grows at a rate greater than 0.5 cm/ 6 months. The treatment is endovascular repair unless the anatomy is unfavorable (unusual). You should see a board certified vascular surgeon with endovascular experience.