An aortic aneurysm is a bulge in the wall of the aorta, the largest blood vessel in your body. The aorta runs from your heart down through your chest and abdomen, delivering blood to every major organ. When a section of this vessel wall weakens, it can balloon outward, creating a pocket that grows over time and, in serious cases, can rupture. Most aortic aneurysms produce no symptoms at all, which is why they’re often discovered by accident during imaging for something else entirely.
Where Aneurysms Form
Aortic aneurysms are classified by location. An abdominal aortic aneurysm (AAA) forms below the chest, typically in the section running through the belly. This is the more common type. A thoracic aortic aneurysm (TAA) forms in the chest portion of the aorta, either near where the vessel leaves the heart (the ascending aorta) or further along as it curves downward (the descending aorta). Some people develop aneurysms in both regions.
The distinction matters because the two types differ in who they affect, how they’re monitored, and when surgery becomes necessary.
Why the Aortic Wall Weakens
The aorta has a layered wall, and the middle layer provides most of its structural strength. In an aneurysm, that middle layer breaks down. The smooth muscle cells that give the wall its shape die off, and the proteins that hold the wall together (especially elastin and collagen fibers) get degraded by enzymes the body’s own immune system produces. Inflammation plays a central role: immune cells infiltrate the vessel wall and release chemicals that chew through its architecture.
This process happens gradually, often over years or decades. The wall thins, loses elasticity, and starts to stretch under the constant pressure of blood flow. Once it begins to bulge, the physics work against you. A wider vessel experiences more wall stress at the same blood pressure, which accelerates further expansion.
Risk Factors
Smoking is the single strongest modifiable risk factor. It damages blood vessel walls directly and accelerates the inflammatory process that leads to aneurysm formation. Other major contributors include high blood pressure, which increases the mechanical stress on the aortic wall, and atherosclerosis (plaque buildup in the arteries).
Age is a significant factor. Most aortic aneurysms are diagnosed in people over 60, and abdominal aneurysms are far more common in men than in women. Having a first-degree relative with an aortic aneurysm also raises your risk substantially.
Certain inherited connective tissue disorders create an elevated risk at younger ages. People with Marfan syndrome, Loeys-Dietz syndrome, or vascular Ehlers-Danlos syndrome have genetic changes that weaken connective tissue throughout the body, including the aortic wall. For these individuals, aneurysms can develop earlier in life and at smaller diameters, so guidelines recommend more aggressive surveillance with imaging from head to pelvis at baseline and annually thereafter.
Symptoms and Why Most Go Unnoticed
Abdominal aortic aneurysms often grow slowly and produce no symptoms for years. Many start small and stay small. When a growing AAA does cause symptoms, the most common signs are a deep, constant pain in the belly or side, back pain, and a throbbing or pulsing sensation near the belly button. Thoracic aneurysms may cause chest pain, shortness of breath, hoarseness, or a cough, though many of these are also silent.
The danger is that the first symptom can be a rupture. A ruptured abdominal aortic aneurysm is always fatal without emergency treatment and remains highly lethal even with it. This is why screening and monitoring matter so much.
Rupture vs. Dissection
These are two different emergencies, and both involve the aortic wall failing. A rupture means the wall tears completely through, allowing blood to leak into the surrounding body cavity. An aortic dissection is different: the inner lining of the aorta separates from the middle layer, and blood forces its way between these layers, creating a false channel within the wall itself. A dissection can occur in an aneurysm, but it can also happen in an aorta of normal size. Both are life-threatening and require immediate emergency care.
Screening Recommendations
Because most aneurysms are silent, screening with a simple abdominal ultrasound can catch them before they become dangerous. The U.S. Preventive Services Task Force recommends a one-time screening ultrasound for men aged 65 to 75 who have ever smoked. Men in that age range who have never smoked may still benefit from selective screening based on other risk factors. For women who have never smoked and have no family history, routine screening is not recommended. For women aged 65 to 75 who have smoked or have a family history, the evidence on screening benefits is still considered insufficient to make a firm recommendation.
How Aneurysms Are Monitored
An abdominal aortic aneurysm is formally diagnosed when the aorta measures wider than 3.0 cm on ultrasound. But that doesn’t automatically mean surgery. Small aneurysms are monitored with periodic imaging, and the schedule tightens as the aneurysm grows.
- 3.0 to 3.9 cm: Longer intervals between scans are considered safe, often every two to three years.
- 4.0 to 4.9 cm: Growth rates increase, so annual ultrasound surveillance is standard.
- 5.0 cm and above in men (4.5 cm in women): Scans every six months, and surgical repair becomes a serious consideration.
For thoracic aneurysms, the main trigger for surgery is a diameter of 5.5 cm or greater in the ascending aorta, though many experienced surgical teams will operate selectively at 5.0 to 5.4 cm. Rapid growth, defined as 0.5 cm or more in a single year, is an indication for surgery regardless of the current size.
Women tend to rupture at smaller diameters than men. The average size at rupture is 5.0 cm in women compared to 6.0 cm in men, which is why lower thresholds are used for female patients.
Surgical Repair
When an aneurysm reaches the size threshold for intervention, there are two main surgical approaches. Open repair involves a large incision, where the surgeon replaces the weakened section of aorta with a synthetic graft. It’s a major operation with a longer recovery.
The less invasive option, called endovascular aneurysm repair (EVAR), works through small punctures near the groin. A catheter is threaded through the femoral arteries up to the aneurysm, where a fabric-lined metal stent graft is deployed inside the vessel. This graft creates a new inner lining that takes the pressure off the weakened wall, reducing the risk of rupture. Real-time imaging guides the catheter into position. Recovery from EVAR is typically faster, with a shorter hospital stay and less pain. Not everyone’s anatomy is suited for the endovascular approach, so the choice depends on the aneurysm’s shape, location, and the patient’s overall health.
Living With an Aortic Aneurysm
If you’ve been diagnosed with an aneurysm that’s being monitored rather than surgically repaired, lifestyle adjustments can slow its growth and reduce the risk of complications. Blood pressure control is the top priority. The target is generally at or below 130/80, since every point of excess pressure adds stress to the weakened wall.
Moderate physical activity is encouraged. Walking, biking, swimming, dancing, and light jogging are all generally safe. What you should avoid is anything that causes sudden spikes in blood pressure: lifting anything heavier than 30 pounds, shoveling snow, chopping wood, or using heavy equipment like sledgehammers. Competitive and contact sports are off the table, and so are amusement park rides that subject the body to high G-forces. After surgery, the weight limit drops to 10 pounds during recovery.
If you smoke, quitting is the single most impactful change you can make. Smoking accelerates aneurysm growth and dramatically increases the risk of rupture. For people with connective tissue disorders, smoking cessation and blood pressure control are especially critical, since these conditions already predispose the aorta to events at smaller sizes and younger ages.