An aneurysm is a swelling of an artery which usually develops over a period of years. Although aneurysms can affect any artery, they most commonly occur in the abdominal aorta just above the belly button. There are called Abdominal Aortic Aneurysms (AAA) and occur in 5% of men over 60 years of age.
The natural course of aortic aneurysms is to gradually enlarge. They do not usually cause any symptoms. However after they reach about three times the normal diameter of the aorta they carry an increasing risk of rupture. The rupture of an aortic aneurysm causes massive internal bleeding. AAA is caused by the weakening of the artery wall. Risk factors for developing AAA are family history, high blood pressure and smoking. They arise more commonly in men.
Because they are usually asymptomatic, aneurysms are normally detected incidentally during a routine examination or after having tests for other conditions. There is good evidence that detecting and treating aneurysms earlier through screening with ultrasound reduces the risk of death from aneurysm rupture.
The risk of aneurysm rupture is directly related to its size. It is generally recommended that aneurysms below 5cm in diameter are not treated immediately but monitored until they enlarge to 5.5cm. This is called watchful waiting; the rationale is not to subject patients to the risks of surgical repair until the risk of rupture is at least 5% per year. The average growth rate for aneurysms is 3mm per year.
Treatment of aortic aneurysm involves either replacing the swollen artery with a graft sewn inside the aorta (open surgical repair) or inserting a stent graft inside the aneurysm by minimally invasive endovascular techniques (endovascular aneurysm repair or EVAR).