What is an aortic aneurysm?
Finding out you have an aortic aneurysm can feel alarming. The word "aneurysm" sounds serious, and it is a condition worth taking seriously. But for most people who are diagnosed, the aneurysm is small, growing very slowly, and does not need treatment right away. Understanding what it is helps put things in perspective.
The aorta is the main artery in the body. It runs from the heart, through the chest, and down through the abdomen, delivering blood to every organ and limb. The aorta normally measures about 2 cm across in the abdomen, roughly the width of a thumb. An aneurysm forms when a section of the aorta wall weakens and begins to bulge outward, like a weak spot in a hosepipe.
A diagnosis of aortic aneurysm is made when the diameter of the aorta exceeds 3 cm. Aneurysms are most commonly found in the lower part of the abdomen, below the kidneys. These are called abdominal aortic aneurysms, or AAA. Aneurysms can also occur in the chest (thoracic aneurysms) or span both regions (thoracoabdominal aneurysms).
Diagram: aortic aneurysm explained
Diagram for illustration only. Not a clinical image.
What causes an aortic aneurysm?
The most common underlying cause is atherosclerosis: the same process of fatty plaque deposition that causes coronary artery disease and peripheral arterial disease. Over time, this weakens the elastic fibres in the aorta wall, allowing it to gradually expand.
The most important risk factors are:
- Smoking: by far the strongest modifiable risk factor. Smokers are four to five times more likely to develop an aortic aneurysm than non-smokers
- Age: the risk rises steeply after 65, as decades of arterial wear accumulate
- Male sex: men are four to five times more likely to develop an AAA than women, though women tend to develop aneurysms at smaller sizes and with a higher rupture risk at any given diameter
- High blood pressure: sustained elevated pressure accelerates wall degeneration
- Family history: having a first-degree relative with an aortic aneurysm approximately doubles your risk
- Connective tissue disorders: Marfan syndrome, Loeys-Dietz syndrome and Ehlers-Danlos syndrome all predispose to aortic aneurysms, often at a younger age
Aneurysms can also result from aortic dissection, infection (mycotic aneurysm), or inflammation (inflammatory aneurysm), though these are much less common.
Does an aortic aneurysm cause symptoms?
The majority of aortic aneurysms cause no symptoms at all. Most are found incidentally when a scan is done for an unrelated reason, such as a kidney investigation or a check of the heart. This is one reason the NHS offers ultrasound screening to men aged 65 in England.
When symptoms do occur, they may include:
- A persistent deep aching pain in the abdomen or lower back
- A pulsating or throbbing sensation in the abdomen, which some people notice when lying down
- Feeling full quickly after eating, if a large aneurysm is pressing on nearby structures
NHS screening and how aneurysms are found
In England, all men are invited for a free NHS abdominal aortic aneurysm ultrasound scan during the year they turn 65. The scan is simple, painless and takes around 10 to 15 minutes. Women are not currently offered routine screening, as the prevalence of AAA in women is considerably lower, though the repair threshold is smaller (5.0 cm rather than 5.5 cm) because rupture risk is higher in women at any given diameter.
Men over 65 who were not previously screened can self-refer to their local NHS screening programme. Those with a family history or connective tissue disorder may be offered earlier surveillance.
How aneurysm size guides surveillance and treatment
The single most important factor in managing an aortic aneurysm is its size. The larger it grows, the greater the risk of rupture. The relationship is not linear: rupture risk rises steeply once the aneurysm exceeds 5 to 5.5 cm.
Repair is also considered regardless of size if the aneurysm is growing by more than 1 cm per year, is causing symptoms, or is tender on examination. Women are typically referred at 5.0 cm rather than 5.5 cm. The decision to repair is always made jointly by the patient and the vascular team, taking fitness for surgery, anatomy and individual preference into account.
Treatment options
When an aneurysm reaches the repair threshold, there are two main approaches: endovascular repair and open surgery. The choice depends on the anatomy of the aneurysm, the patient's fitness, and where the aneurysm extends to.
Endovascular aneurysm repair (EVAR)
EVAR is a keyhole procedure performed through small cuts in the groin. Under X-ray guidance, a catheter is passed through the femoral arteries and a stent-graft (a fabric tube supported by a metal framework) is deployed inside the aneurysm. The graft sits within the aorta and takes over the job of carrying blood, effectively sealing the aneurysm off from the circulation so it cannot rupture.
EVAR is performed under general or regional anaesthetic. Most patients spend one to two nights in hospital and can return to light activity within two to four weeks. The procedure has a lower 30-day mortality than open repair and is suitable for the majority of infrarenal AAAs with suitable anatomy.
EVAR does require lifelong surveillance with CT or ultrasound scans, typically annually, to check that the stent-graft remains in the correct position and has not developed a leak (known as an endoleak). Some patients need additional procedures over the years to maintain the repair. This is the main trade-off compared to open surgery.
Open surgical repair
Open repair involves a incision in the abdomen to expose the aorta directly. The diseased segment is opened, and a synthetic graft is sewn in place to replace it. The operation is performed under general anaesthetic and typically takes three to five hours.
Open repair requires a longer recovery than EVAR, typically five to ten days in hospital and six to twelve weeks before returning to normal activity. The 30-day mortality is slightly higher than EVAR, particularly in older or less fit patients. However, open repair is highly durable and, once healed, does not require ongoing surveillance imaging in most cases.
Open repair remains the preferred approach for younger, fitter patients with complex anatomy that is not suitable for EVAR, and for aneurysms involving the kidney arteries (juxtarenal or suprarenal AAA), where standard EVAR devices do not reach.
Fenestrated and branched EVAR (FEVAR and BEVAR)
When an aneurysm extends close to or above the kidney arteries, standard EVAR devices cannot be used safely. Fenestrated EVAR uses a custom-made stent-graft with precisely positioned holes (fenestrations) or branches that allow blood to continue flowing into the kidney and visceral arteries while the aneurysm is sealed. These grafts are manufactured to each patient's anatomy using their CT scan measurements.
FEVAR and BEVAR are highly specialist procedures performed at major aortic centres. They extend the endovascular option to patients who would previously have required complex open surgery. Results at experienced centres are excellent, though the procedures carry higher complexity and longer planning times than standard EVAR.
What happens if an aortic aneurysm ruptures?
Rupture is the main danger of an untreated aneurysm. When the aortic wall gives way, bleeding occurs rapidly into the abdomen. Without immediate surgery, rupture is almost always fatal. Even with emergency surgery, overall survival from a ruptured AAA is approximately 20% when accounting for those who do not reach hospital in time. For those who reach an operating theatre, survival rates at specialist centres have improved significantly with emergency EVAR, but remain approximately 30 to 40%.
This stark prognosis is precisely why elective repair, done before rupture, is so strongly recommended once an aneurysm reaches the threshold. A planned operation at an experienced centre carries a 30-day mortality of around 1 to 2% for EVAR and 3 to 5% for open repair in fit patients, compared to the far greater risk of rupture left untreated.
Living with an aortic aneurysm under surveillance
Most people diagnosed with a small or medium aneurysm will spend months or years on surveillance. This is not a passive process. There are things you can do to slow the growth of the aneurysm and reduce your overall cardiovascular risk:
- Stop smoking: this is the single most effective thing you can do. Smoking dramatically accelerates aneurysm growth and rupture risk
- Control blood pressure: aim for a systolic blood pressure below 130 mmHg. Your GP can help with medication if lifestyle measures are not sufficient
- Take your medications: a statin and antiplatelet medication are often recommended to reduce overall cardiovascular risk
- Attend all your surveillance scans: missing a scan means a potential change in size goes undetected
- Know the warning signs: sudden severe back or abdominal pain is an emergency
Very strenuous physical activity, such as heavy weightlifting, raises intra-abdominal pressure briefly and is generally not recommended for people with medium or large aneurysms. Moderate exercise such as walking is safe and beneficial.
What to do next
If you have been told you have an aortic aneurysm and want to understand your options, or if you have concerns about surveillance, a private vascular consultation can provide a prompt specialist opinion and review of your imaging. You do not need a GP referral for a private appointment.
If you have a family history of aortic aneurysm and have not been screened, speak to your GP or consider a private ultrasound screening scan. Early detection is the key to preventing rupture.
Sources and further reading
- ESVS 2024 Clinical Practice Guidelines on the Management of Abdominal Aorto-iliac Artery Aneurysms.
- NHS Abdominal Aortic Aneurysm Screening Programme.
- NHS. Abdominal aortic aneurysm.