Reviewed for medical accuracy by Dr Evelyne Jonniaux, Medical Advisor
Last updated 17 September 2026
Below 5.5 cm, operating on an abdominal aortic aneurysm brings no survival benefit. This is a high-certainty result, true at any age and at any diameter within the 4 to 5.5 cm range, and it holds even when operative mortality is excellent.
The questions we get asked
Why not operate straight away?
Because four randomised trials pooled across 3,314 patients give a hazard ratio of 0.99, at high certainty. In other words, nothing. The American ADAM trial is the most telling, because its operative mortality was only 2.7 percent and the result still leaned numerically against early surgery.
One striking figure from the British twelve-year follow-up: three quarters of the surveillance group ended up being operated on, and their operative mortality was no higher than that of those operated immediately. Surveillance does not cost anyone their chances; it spares operations to those who will never need one.
How often should it be scanned?
Rupture risk is multiplied by 1.91 for each additional half centimetre of diameter. To keep rupture risk below 1 percent between two checks, the interval falls from 8.5 years at 3 cm to 17 months at 5 cm. That is what justifies tightening surveillance as the diameter grows.
Endovascular repair or open surgery?
Endovascular repair has a real and uncontested early advantage: 1.7 percent mortality at 30 days against 4.7. That advantage disappears within a few years, and it comes with more reinterventions. The Dutch trial measures 16.7 points of difference in freedom from reintervention at twelve years.
Beyond eight years the trials contradict each other head-on, and that has to be said. The British trial finds higher late mortality after endovascular repair, with secondary sac rupture as the identified driver. The American trial finds the opposite trend and writes so explicitly in its own abstract. The Dutch trial finds no survival difference.
Is ultrasound screening useful?
The British randomised trial gives a 42 percent reduction in aneurysm-related mortality over thirteen years. That is solid. But the other two figures from the same trial deserve stating: the reduction in all-cause mortality is 3 percent, and 216 men must be invited to prevent one death.
A Swedish cohort, observational and contested, raises a legitimate question: aneurysm mortality fell from 36 to 10 per 100,000 between the early 2000s and 2015, at the same rate in counties with and without a screening programme. The absolute benefit measured in 1997 may no longer be the same today.
What the figures say
| Finding | Figure | Source |
|---|---|---|
| Early surgery against surveillance below 5.5 cm | hazard ratio 0.99, high certainty | Cochrane, 2020 |
| Ruptures under surveillance, 4 to 5.4 cm | 0.6 percent per year | ADAM trial, N Engl J Med, 2002 |
| 30-day mortality, endovascular against open | 1.7 against 4.7 percent | EVAR-1, Lancet, 2004 |
| Freedom from reintervention at 12 years | 16.7 points favouring open surgery | DREAM, J Vasc Surg, 2017 |
| Screening, aneurysm mortality at 13 years | reduced by 42 percent | MASS trial, Br J Surg, 2012 |
| Men to invite to prevent one death | 216 | MASS, 2012 |
Three widespread figures we could not source. “A 5.5 cm aneurysm has a 10 percent annual rupture risk”: not found in any primary source; the 5.5 cm threshold comes from the absence of benefit to operating below it, not from a measured rate above it. “The 5.5 cm threshold is validated in women”: it is not, and Cochrane explicitly calls for research on this. And “after eight years endovascular repair kills more” is one trial’s result, contradicted by another.
What Noria Health does, and does not do
We organise a vascular surgery consultation with a specialist team near Brussels, including review of existing imaging, and confirm feasibility within 24 to 48 hours.
We do not measure an aneurysm remotely, we do not set a surgical indication, and we never recommend spacing out surveillance already under way. Sudden abdominal or back pain in someone with a known aneurysm is an emergency: call emergency services, do not wait for a reply from us.
Who reviewed this page
Noria Health editorial team.
See also: all our articles on vascular surgery.
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