Abdominal Aortic Aneurysm

Vascular AAA

A balloon-like bulge in the main artery as it passes through the belly — usually silent until it leaks or bursts.

Educational summary only — not medical advice, and no substitute for assessment by a clinician. Diagrams are simplified illustrations.

A weakened patch of the aorta stretches into a balloon; the wider it grows, the thinner and more rupture-prone the wall becomes.

Overview

An aneurysm is a balloon-like bulge that forms where an artery wall has weakened. An abdominal aortic aneurysm is a bulge in the section of the aorta running down through the belly. Most cause no symptoms and are found by chance — which is dangerous, because the first sign can be a sudden, life-threatening rupture.

How the system normally works

The abdominal aorta is a thick-walled, high-pressure pipe about 2 cm wide that delivers blood to the abdomen, kidneys and legs. Its elastic wall normally holds a steady diameter despite the constant pulse of blood.

What goes wrong

Years of wear — high blood pressure, smoking, ageing, and inflammation — weaken the wall. Under relentless pressure the weak spot stretches outward. Like an over-inflated balloon, a wider wall is also a thinner one (the physics of wall tension), so as the bulge grows the risk of tearing rises steeply. Slow-flowing blood inside can also form clot that occasionally throws fragments downstream.

Side-by-side diagram comparing a normal abdominal aorta with an aneurysmal one showing a balloon-like bulge. — Aneurysms are judged by diameter: a normal aorta is about 2 cm wide; risk of rupture climbs steeply once the bulge passes about 5–5.5 cm.

Symptoms and why they happen

Usually none — most are silent and discovered incidentally.
Sometimes a deep, throbbing or pulsing sensation in the belly.
Steady belly, flank, or lower-back pain — a stretching or enlarging wall.
A pulsatile lump near the navel that a clinician may feel.
New, severe pain can mean rapid expansion or impending rupture.

Causes and risk factors

Smoking (the strongest modifiable risk)
High blood pressure and atherosclerosis
Male sex and age over 65
Family history of aneurysm
Connective-tissue disorders

How it's diagnosed

Ultrasound is simple, accurate and used for screening (many countries offer a one-time scan to older men). CT gives precise size and anatomy when planning repair. Size and growth rate guide decisions.

Diagram of a ruptured abdominal aortic aneurysm with blood escaping from the torn, ballooned wall into the abdomen. — Rupture is the feared event: the thin wall tears and blood pours into the abdomen — immediately life-threatening.

Treatment and management

Small aneurysms are monitored with regular scans, alongside stopping smoking and controlling blood pressure and cholesterol. Once the bulge reaches about 5.5 cm (or grows quickly, or causes symptoms), repair is advised — either keyhole placement of a stent-graft lining the aorta (EVAR) or open surgical replacement with a graft.

Possible complications

The dominant complication is rupture, which is frequently fatal before reaching hospital. Clot from the aneurysm can also block arteries to the legs.

Prevention and outlook

Not smoking is the single most important preventive measure, with blood-pressure and cholesterol control close behind. Planned repair of a large aneurysm has a far better outlook than emergency surgery for a rupture — which is why screening and monitoring matter.

When to seek emergency care

Sudden severe belly or back pain with faintness or collapse — possible rupture; call emergency services.
A known aneurysm with any new pain — seek urgent assessment.