Screening for a condition is basically performing a test on a large number of people who might get that condition, to try to find which of them are affected - and which are not.

For screening to be successful and worthwhile, there are several things that need to be true:

• The condition being screened for needs to be a serious health risk
• The condition needs to be common enough to be worth screening for
• There needs to be an effective cure if it is found
• The test to find it needs to be accurate
• The test needs to be safe
• The test needs to be inexpensive

No condition fits all of these points perfectly, but aneurysms fit very well for a condition that needs screening. This is because:

• If aortic aneurysms rupture (burst), only half of patients get into hospital alive and only half of those survive emergency surgery
  If popliteal aneurysms thrombose (block off), about half the patients will lose their legs
   
• Aortic aneurysms kill at least 10,000 patients in the UK every year - and many more have surgery to prevent ruptures - showing aortic anurysms are common enough to screen for
  Popliteal aneurysms are much less common; but the test is the same and there is a link between people who get aortic and popliteal aneurysms - so it would be stupid not to screen for these at the same time
   
• Surgery for aortic and popliteal aneurysms cure the condition. Success rates rates for elective surgery (ie: in those where the aneurysm is found before it becomes an emergency) are far better.
  Survival for elective aortic aneurysm repair is about 90 - 95% (rather than 25% for rupture at home - see above)
  Success for elective bypass grafting for popliteal aneurysm is about 90% at one year (rather than 50% for emergency bypass)
   
• Ultrasound is accurate, safe and - compared to the risk of not finding the aneurysm - is inexpensive  

Therefore screening for aneurysms is clearly a sensible way forward - but only if it is done in people who are at risk of getting an aneurysm.