Approximately 70 to 75% of abdominal aortic aneurysm are asymptomatic when first detected. Average growth of a small aneurysm is around 0.25 cm in diameter per year. One other study lists the growth rate at 0.32 cm per year when it is under 5 cm. As it gets larger, it may grow as much as 0.4 cm to 0.5 cm per year.