An aneurysm is a bulge in an artery wall that weakens over time
An aneurysm is a section of an artery that has stretched and thinned, creating a balloon-like pouch. Blood pressure pushes outward on this weakened spot continuously. The wall gets thinner as it expands, which makes it more fragile. If the bulge ruptures, blood spills into surrounding tissue—a medical emergency that can cause severe bleeding, organ damage, or death depending on where the aneurysm is located.
Most aneurysms develop silently over years without any symptoms. A person can have one and not know it. Others are found by accident during imaging tests done for unrelated reasons. The danger lies in the rupture risk: a small aneurysm might never break, but a larger one carries higher risk, especially if it continues to grow.
Key Takeaways
- An aneurysm is a weakened, bulging section of an artery that can rupture and cause life-threatening bleeding.
- Most aneurysms cause no symptoms and are discovered only through imaging tests or screening.
- High blood pressure, smoking, and family history are the main factors that increase aneurysm risk.
- Treatment depends on the aneurysm's size, location, and growth rate, ranging from monitoring to surgery.
- A ruptured aneurysm is a medical emergency requiring immediate hospital care.
Where aneurysms form and why location matters
Aneurysms can develop in any artery, but certain locations are more common and more dangerous. The abdominal aorta—the large vessel carrying blood from the heart to the lower body—is the most frequent site. Cerebral aneurysms in the brain are less common but often more serious because rupture can cause stroke or permanent brain damage. Aneurysms also occur in arteries of the legs, chest, and behind the knees.
Location determines what happens if rupture occurs. A ruptured abdominal aortic aneurysm causes massive internal bleeding into the abdomen. A ruptured cerebral aneurysm bleeds into the space around the brain, causing sudden severe headache, neck stiffness, and loss of consciousness. A ruptured aneurysm in the leg causes bleeding into the limb and loss of blood flow downstream. The larger the artery involved, the faster blood loss can become life-threatening.
What causes the artery wall to weaken
High blood pressure is the leading cause of aneurysm formation. Constant pressure against artery walls damages the inner lining and weakens the muscular layer underneath. Over time, this damage accumulates and the wall begins to bulge. Smoking accelerates this process by damaging blood vessel walls directly and raising blood pressure.
Family history plays a significant role—people whose parents or siblings had aneurysms face higher risk. Certain genetic conditions that affect connective tissue, such as Marfan syndrome and Ehlers-Danlos syndrome, make aneurysm formation much more likely. Age is also a factor: aneurysms become more common after age 60, though they can develop at any age. Chronic inflammation of arteries, atherosclerosis (plaque buildup), and previous arterial injury can all contribute to weakening.
Symptoms you might notice, or might not
Most small aneurysms produce no symptoms at all. A person feels completely normal and has no warning signs. This is why screening is important for people at high risk—the aneurysm may be growing without their knowledge.
Larger aneurysms sometimes cause symptoms depending on their location and what structures they press against. An abdominal aortic aneurysm might cause deep abdominal or back pain, a pulsing sensation in the abdomen, or flank pain. A cerebral aneurysm that has not ruptured might cause headaches, vision changes, or facial pain if it presses on nearby nerves. A thoracic aortic aneurysm can cause chest or upper back pain. These symptoms do not always mean rupture is imminent, but they warrant immediate medical evaluation.
A ruptured aneurysm causes sudden, severe symptoms: sudden worst headache of life (cerebral), sudden severe abdominal or back pain with shock symptoms (abdominal aortic), or sudden severe chest pain (thoracic). These are medical emergencies requiring immediate hospital care.
How doctors find and measure aneurysms
Aneurysms are discovered through imaging tests. CT scans are the most common method—they create detailed cross-sectional images and can show the exact size and shape of the bulge. Ultrasound is often used for abdominal aortic aneurysms because it is quick, inexpensive, and does not use radiation. MRI provides detailed images and is useful when CT is not suitable. Angiography involves injecting contrast dye into the artery and taking X-rays to visualize blood flow.
Doctors measure the aneurysm's diameter in millimeters. Size determines risk: a 3-centimeter abdominal aortic aneurysm has low rupture risk, while one larger than 5.5 centimeters has much higher risk. Growth rate also matters—an aneurysm that is enlarging rapidly may need intervention sooner than one that is stable. The location and shape of the aneurysm influence whether surgery is technically possible and safe.
Treatment options depend on size and growth rate
Small, stable aneurysms that are not causing symptoms are usually monitored rather than operated on immediately. Doctors order repeat imaging at regular intervals—every 6 to 12 months, depending on size—to track whether the aneurysm is growing. During monitoring, controlling blood pressure and quitting smoking become critical to slow progression. This approach avoids surgery risks for aneurysms that may never rupture.
Surgery or catheter-based intervention becomes necessary when the aneurysm reaches a certain size threshold, grows rapidly, causes symptoms, or ruptures. Open surgical repair involves making an incision, clamping the artery above and below the aneurysm, and replacing the weakened section with a synthetic graft. Endovascular repair is less invasive: a catheter is threaded through an artery to the aneurysm site, and a stent-graft is deployed to reinforce the weakened wall from inside. Recovery is faster with endovascular repair, but not all aneurysms are suitable for this approach.
For cerebral aneurysms, treatment options include clipping (surgical placement of a metal clip across the aneurysm neck to stop blood flow into it) or coiling (catheter-based placement of platinum coils inside the aneurysm to promote clotting). The choice depends on the aneurysm's shape, location, and the patient's overall health.
Reducing your risk if you are at higher risk
Controlling blood pressure is the single most important step. This means taking prescribed blood pressure medications consistently, limiting salt intake, maintaining a healthy weight, and exercising regularly. Even modest reductions in blood pressure can slow aneurysm growth.
Quitting smoking stops further damage to artery walls and reduces the rate of aneurysm expansion. People with a family history of aneurysm should discuss screening with their doctor—screening may be recommended even without symptoms. Managing other cardiovascular risk factors like high cholesterol and diabetes also helps protect artery health. Avoiding heavy lifting and straining can reduce sudden pressure spikes in the abdomen and chest.
Frequently Asked Questions
Can an aneurysm go away on its own?
No. Once an aneurysm forms, the weakened section does not repair itself. It may stay the same size for years, grow slowly, or grow rapidly, but it will not shrink or heal. This is why monitoring and controlling risk factors are important—they slow growth but do not eliminate the aneurysm.
How fast do aneurysms usually grow?
Growth rates vary widely. Some aneurysms remain stable for years without changing size. Others grow a few millimeters per year. A few grow rapidly. Doctors track growth through repeat imaging and adjust the monitoring schedule or recommend treatment based on how quickly the aneurysm is enlarging.
What is the difference between an aneurysm and a blood clot?
An aneurysm is a bulging weakness in the artery wall itself. A blood clot is a solid mass of blood that forms inside a vessel and can block blood flow. They are different problems requiring different treatments, though a blood clot can form inside an aneurysm.
If I have an aneurysm, will I definitely have a stroke or heart attack?
No. Many people live for years with stable aneurysms that never rupture. Risk depends on size, location, growth rate, and whether you control blood pressure and other risk factors. Your doctor can discuss your individual risk based on these factors.
Is surgery always necessary if an aneurysm is found?
Not always. Small, stable aneurysms that are not causing symptoms are typically monitored with repeat imaging rather than operated on immediately. Surgery becomes necessary when the aneurysm reaches a certain size, grows rapidly, causes symptoms, or ruptures. Your doctor will discuss whether monitoring or intervention is appropriate for your situation.