Abdominal aortic aneurysm

The aorta is the largest blood vessel in the body: it leaves the heart, runs down through the chest into the abdomen and from there distributes blood to every organ. When a stretch of its wall in the abdomen loses strength, it gradually balloons out into a sac. That is an abdominal aortic aneurysm. While it stays small, a person carries on with ordinary life and suspects nothing. The danger lies elsewhere: a stretched wall may one day fail to hold the pressure.

What happens to the vessel wall

A healthy abdominal aorta in an adult is about two centimetres across. It is called an aneurysm once it reaches three centimetres or more. The cause is not the vessel getting "clogged" but the breakdown of the elastin and collagen fibres that keep the wall taut. The wall grows thinner and more pliable, and from then on plain physics takes over: the wider the tube, the harder the pressure inside pushes it outwards. That is why a large aneurysm grows faster than a small one, not slower. On average it gains a couple of millimetres a year, and that slowness is exactly what misleads people: more than a decade often passes between the aneurysm forming and the point where it becomes dangerous.

The signs that do get noticed

In most people an aneurysm produces nothing at all. It turns up by chance, on an abdominal ultrasound ordered for something else or on a scan.

Once the widening becomes substantial, you may notice:

• a dull, deep ache in the abdomen, the lower back or the flank, unrelated to meals and not relieved by shifting position;
• a throbbing or pulsing sensation in the belly, especially when lying on your back;
• feeling full after only a small meal, if the aneurysm presses on the stomach.

None of these proves an aneurysm: a slipped disc, kidney stones or bowel disease produce the same thing. But abdominal or back pain that lasts for weeks or keeps returning is worth taking to a doctor, and worth an ultrasound.

Rupture: when minutes decide

In a ruptured aneurysm, blood leaves the circulation for the abdominal cavity within minutes. More than half of those affected never reach hospital alive. There is nothing to soften here: call the emergency services straight away, without waiting to see whether it passes.

Call an ambulance if someone has:

• sudden, severe pain in the abdomen, back or side that cannot be endured;
• that pain together with cold sweat, weakness or dizziness;
• pale, grey or ashen skin; on darker skin this shows more clearly on the palms, the soles and the lips;
• a fast weak pulse, confusion, loss of consciousness;
• breathing that has become irregular or has stopped.

Less often the rupture goes not outwards but into a neighbouring organ. Breaking into the duodenum causes vomiting of blood or black stools; breaking into the inferior vena cava causes sudden breathlessness and rapidly swelling legs. Both are equally lethal.

Who is most at risk, and what gets overlooked

An aneurysm usually forms after years of damage to the vessel wall. The odds are higher if a person:

• is a man over 65 — aneurysms are several times more common in men;
• smokes or used to smoke, by far the strongest factor anyone can change;
• lives with high blood pressure;
• has atherosclerosis, coronary artery disease or narrowed leg arteries;
• has chronic obstructive pulmonary disease;
• has a brother, sister or parent with an aortic aneurysm — the risk then rises markedly, whatever the age.

There are also rare causes worth knowing about, because they change the whole approach. Inherited connective tissue disorders — Marfan syndrome, vascular Ehlers-Danlos syndrome, Loeys-Dietz syndrome — cause aneurysms in people in their thirties and forties and call for monitoring from a young age. An infected aneurysm forms when bacteria in the bloodstream settle in the vessel wall: it grows over weeks rather than years, comes with fever and raised inflammatory markers, and is treated as an emergency. The same group includes inflammation of the large arteries, such as Takayasu arteritis and giant cell arteritis. If an aneurysm is found in a young person, or if it has suddenly enlarged, these possibilities are investigated separately.

How it is found and measured

The main test is an abdominal ultrasound: painless, about fifteen minutes, no radiation, and an accurate measurement of the diameter. The result is usually given at the end of the appointment.

By size, aneurysms fall into three groups, and everything that follows depends on the group:

• small — 3 to 4.4 cm;
• medium — 4.5 to 5.4 cm;
• large — 5.5 cm or more.

A small one is normally rechecked once a year, a medium one every three to six months. Skipping those appointments is risky: the point of surveillance is precisely to catch the moment when growth speeds up. Before an operation a contrast scan is added, showing the shape of the aneurysm and the state of the neighbouring arteries.

In a number of countries men are offered a single ultrasound of the aorta at 65. Where no such programme exists, it is reasonable to ask for the scan yourself, particularly with a smoking history or a family history.

Watch or operate

A small aneurysm is not operated on: the risk of surgery outweighs the risk of rupture. It is monitored while the blood vessels are looked after as a whole. Blood pressure medication and statins are usually prescribed, not because they halt the aneurysm's growth (the evidence for that is thin), but because someone with an aneurysm almost always has other vascular problems, and it is those that most often shorten life.

Repair is discussed once the diameter reaches 5.5 cm, once the aneurysm gains more than a centimetre in a year, or once it starts to hurt. Women are often offered it earlier, at around 5 cm: at the same diameter their aneurysms rupture more often.

There are two techniques. In open surgery the damaged stretch is replaced with a synthetic graft — major surgery with a long recovery, but a result that lasts for decades. In the endovascular approach a stent graft is threaded up through the arteries in the groin and opened inside the aneurysm; it is easier to get through, but it requires lifelong imaging checks, because the graft can shift or start to leak. The choice depends on the anatomy of the vessels, on age and on other illnesses, and it is always discussed with a vascular surgeon.

What is in your hands

The one measure with proven effect on how fast an aneurysm grows is stopping smoking completely. In smokers aneurysms grow faster and rupture more often, and the difference shows within the first years of quitting. Everything else works on the vessels in general: steady blood pressure, less salt and less processed meat, losing weight if there is excess, moderation with alcohol.

Staying active with an aneurysm is both possible and advisable: walking, swimming and cycling are safe and good for you. Restrictions normally apply only to maximal strength efforts with the breath held, and those are worth discussing separately with your doctor.

Online consultation: what to bring to it

An Oladoctor doctor can go through your ultrasound or scan report by video call, explain what a particular diameter figure means and advise when the next check should be booked. A consultation makes sense if the aneurysm was found by chance and the next step is unclear; if there has been an aortic aneurysm in the family and you want to know whether you should be screened; if surgery has been proposed and you want to work calmly through the risks of each technique.

The online format is not for an acute situation. With sudden severe abdominal or back pain, loss of consciousness or sudden pallor, do not spend time writing messages — call the emergency services.

This material is for information only and does not replace medical advice.