Should we screen for aortic aneurysm? NoBMJ 2008; 336 doi: http://dx.doi.org/10.1136/bmj.39514.494167.AD (Published 17 April 2008) Cite this as: BMJ 2008;336:863
The case for screening for abdominal aortic aneurysms looks open and shut. Mortality for patients with a ruptured aneurysm is around 90% if you include those who do not survive until the ambulance arrives.1 2 But if the aneurysm is discovered before it ruptures and is repaired electively, the mortality in the hand of an experienced vascular surgeon is around 7.4% in England.3 Unfortunately abdominal aortic aneurysms rarely give rise to symptoms and so are not diagnosed before they rupture. Screening would ensure that most aneurysms in the appropriate age group will be picked up and could be repaired electively.
The UK government seems convinced, and pilot screening programmes for men aged 65 are due to be launched this year. But I believe this move is overhasty. The average mortality for surgical repair, which comes from an epidemiological survey of 112 545 diagnoses or repairs,3 hides wide variations between hospitals. In addition, the headline case fatality rate is higher in England than that reported in most other countries.4 Specialist centres providing 24 hour access to vascular surgeons and radiologists trained in emergency endovascular repair would reduce mortality.
My main objection, however, is that I’m uneasy about taking people off the street who think they are perfectly well and subjecting them to a procedure from which 1 in 14 will die. It’s a difficult decision to justify to a grieving family who may well have taken in the positive messages about screening and early treatment without really absorbing the small but real level of risk associated with surgery.
Aneurysms are rather like balloons—the bigger they get the more likely they are to burst. We know that aneurysms with a diameter of less than 5.5 cm are so unlikely to burst that the mortality from operating on them is greater than the likelihood of rupture.5 People who have been screened and found to have an aorta that is dilated less than 5.5 cm will be condemned to six monthly or annual ultrasound examinations to estimate the size of the aneurysm. Some grow, some don’t; and the ones that grow quickly are the most dangerous. The only way to find out is serial measurements. This in itself is straightforward enough, but all vascular surgeons have a cohort of patients who find it intolerable to have what they often describe as a “time bomb” inside them which might go off at any time and without notice.
Feasibility of repair
Even when the aneurysm grows to more than 5.5 cm, what happens next is not always straightforward. Although in an otherwise healthy patient the risk of rupture is greater than that of surgery, aneurysm patients are seldom “otherwise healthy.” An aneurysm is a disease of an artery, and arterial disease rarely exists in isolation. Most patients will have hypertension or a history of myocardial infarction or stroke. Some are diabetic. More often they are heavy smokers and have pulmonary disease. Often comorbidity is discovered during the work-up for aortic surgery, and sometimes the coronary artery disease or lung cancer has to be dealt with first.
So aneurysm screening will turn up much more than aortic aneurysms, and the cost of dealing with the comorbidity needs to be included in the cost-benefit analysis. Many patients will not be fit enough to have a repair and will be left knowing that the time bomb in their abdomen doesn’t just have a remote possibility of exploding but is quite likely to do so soon. Admittedly some, probably more than half, of these high risk patients can be treated with an aortic stent6—a lesser surgical procedure which simply requires access to the femoral arteries by incisions in both groins. The cost effectiveness of this form of treatment is, however, uncertain.7 There is also long term uncertainty about the security of the devices and persistent leaks into the aneurysmal sac (endoleaks).8 So patients with endovascular repairs have a new time bomb in the abdomen—a prosthesis that may come loose or leak (thus revascularising the aneurysm).
In a minority of patients, the configuration of the aneurysm or the condition of the patient makes even endovascular repair impossible. In any case NHS commissioners take very different views about the extent to which they are prepared to purchase endovascular repair saying (incorrectly9) that it is still experimental.
In short, many patients will be left with the knowledge that they have a life threatening condition that is liable to cause sudden death and that nothing can be done about it. It doesn’t affect the arithmetic of lives saved but it is a serious social consequence that needs to be thought through. At the very least, as with HIV, any member of the public taking the test will need intensive counselling about the possible consequences that screening might have for their future lives and psychological wellbeing.
Competing interests: None declared.