Half of all untreated aortic aneurysms rupture within five years. Untreated aortic aneurysms rupture at any time, causing internal bleeding that leads to shock and subsequent death, according to MedicineNet.
The aorta is the largest artery and carries the body's blood supply from the heart to the rest of the body, says MedicineNet. Aortic aneurysms most often occur where the aorta travels down into the abdomen. The aneurysm is a bulge on the side of the aorta, and it grows steadily as pressure forces the blood vessel to expand. The aneurysm often ruptures if it is not treated surgically, and the surgical outcome for an already ruptured aneurysm is poor.