Abdominal Aortic Aneurysm

My 81-year-old husband has been diagnosed with an abdominal aortic aneurysm that?s 4.8 centimeters wide. His doctors say there?s a magic number at which surgery is done, but I?m questioning why they can?t do something sooner. My husband is generally in good health, so he shouldn?t be a poor candidate for surgery.