The aorta is the largest blood vessel in the human body. It carries blood from your heart up to your head and arms and down to your abdomen, legs, and pelvis. The walls of the aorta can swell or bulge out like a small balloon if they become weak. This is called an abdominal aortic aneurysm (AAA) when it happens in the part of the aorta that’s in your abdomen.AAAs don’t always cause problems, but a ruptured aneurysm can be life-threatening. Therefore, if you’re diagnosed with an aneurysm, your doctor will probably want to monitor you closely, even if they don’t intervene right away. Small (less than 5.5 centimeters) or slow-growing AAAsgenerally have a much lower risk of rupture than larger aneurysms or those that grow faster. Doctors often consider it safer to monitor these with regular abdominal ultrasounds than to treat them.Large (greater than 5.5 centimeters) or fast-growing AAAsare much more likely to rupture than small or slow-growing aneurysms. A rupture can lead to internal bleeding and other serious complications. The larger the aneurysm is, the more likely that it will need to be treated with surgery. These types of aneurysms also need to be treated if they’re causing symptoms or leaking blood.