Abdominal aortic aneurysm

3 things to know first

1. It is not cancer. An aneurysm is a swollen, weakened area of a blood vessel, not a tumor.
2. Size matters most. The risk of rupture rises as the bulge gets wider.
3. Most are found by accident. AAA is usually discovered during an ultrasound, CT, or MRI done for another reason.

What it is

The aorta is the main artery that carries blood from the heart down through the chest and abdomen. An abdominal aortic aneurysm (AAA) forms when a section of the wall in the abdominal aorta weakens and balloons outward. Doctors usually call it an aneurysm when the width is 3 cm or larger.

Why it appears on your report

Radiologists describe an AAA on CT, MRI, or ultrasound reports when they measure the aorta in the abdomen and find it wider than expected. The report often gives the largest diameter in millimetres or centimetres — that number is the key detail to watch.

How serious is it?

AAA is usually only dangerous when it is large or growing quickly. Size is grouped into three broad categories:

• Smaller than 3 cm — usually not considered an aneurysm; often a normal variation.
• 3.0–5.4 cm — generally watched with periodic ultrasound or CT. The exact interval depends on the size, growth, and your local guidelines.
• 5.5 cm or larger in men, or 5.0 cm or larger in women — often referred to a vascular surgeon to discuss repair.

These thresholds are guides. Your doctor will also consider your age, body size, blood pressure, and overall health.

When to seek care urgently

Go to emergency care or call emergency services if you have any of the following, especially if you already know you have an AAA:

• Sudden, severe abdominal or back pain
• Dizziness, fainting, or a rapid heartbeat
• Pale, clammy skin
• A pulsating feeling in the abdomen with severe pain

These can be signs of a leaking or ruptured aneurysm and need immediate attention.

What usually happens next

1. Confirm the measurement. Your doctor may order a dedicated vascular ultrasound or CT scan.
2. Review risk factors. Smoking, high blood pressure, male sex, age, and a family history of aneurysm all increase risk and growth.
3. Plan follow-up. Small, stable aneurysms are monitored with regular scans. Larger or fast-growing aneurysms are usually referred to a vascular specialist.
4. Control blood pressure. Good blood-pressure control and not smoking are the most effective ways to slow growth.

A simple analogy

Think of the aorta as a garden hose. If one spot weakens, it can balloon outward like a weak spot in an old hose. A small bulge may hold for years; a large bulge is more likely to burst.

Read more

• NHS — Abdominal aortic aneurysm
• Society for Vascular Surgery — AAA