An aneurysm is a dangerous bulge that forms in the wall of a blood vessel, similar to how a weak spot in a bicycle tire might bulge out when you pump in air. Blood vessels are like tubes that carry blood throughout your body, and normally their walls are strong and smooth. But sometimes a section of wall becomes weak, and the pressure of blood flowing through causes that spot to balloon outward.

Aneurysms are serious because if they grow too large, they can burst, causing dangerous internal bleeding. Doctors can often detect aneurysms before they rupture and treat them with surgery or other medical procedures. Some aneurysms develop because of genetics (traits passed down in families), while others form because of high blood pressure, injuries, or other health conditions.

You might hear about an aortic aneurysm (in the body's largest artery) or a brain aneurysm (in blood vessels in the head). While aneurysms sound frightening, many people live with small ones that doctors simply monitor carefully over time. Modern medicine has become quite good at finding and treating aneurysms before they cause serious harm.