John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. An abdominal aortic aneurysm is a life threatening condition and patients might need lifelong monitoring after treatment. Ultrasonogaphy is sometimes used for this and a new Cochrane Review from June 2017 looks at its accuracy. The review was done by a team from Italy and Kathy Mahan from the Cochrane Neurosciences group, also based in Italy, tells us what they found.

Kathy: Some people with an aneurysm, or weak spot on the main blood vessel from their heart receive endovascular repair, which is done from inside their blood vessels, rather than having surgery in which the chest is opened up. However, after this treatment for their abdominal aortic aneurysm, they may develop a persistent blood flow within the aneurysm called endoleak. This may cause enlargement and rupture of the aneurysm, which will require surgery and could be fatal.
Therefore, patients who have endovascular aneurysm repair need lifetime surveillance to detect potential endoleaks. Computed tomography, or CT scan, is considered the gold standard for this, but there is no agreement about the timing and the number of examinations to be performed. In addition, if CT scans are performed too frequently this raises the possibility of radiation exposition concerns, as well as a cumulative risk of nephrotoxicity due to the use of the contrast agent that is needed to obtain the CT image. Ultrasonography is another tool for monitoring endoleaks. It is less invasive and less costly than CT but is it an acceptable alternative to limit the use of CT scan?
This new Cochrane Review investigates this. It examines whether ultrasonography with or without contrast was accurate in detecting endoleaks in patients who had had endovascular aneurysm repair, when compared to CT scan. And, it finds that contrast-enhanced ultrasonography does provide clinically helpful information and might be a useful alternative to CT scans.
The researchers found 42 studies involving just over 4200 participants. The studies that evaluated ultrasonography without contrast were generally of moderate or low quality, while studies that included the contrast were of high or moderate quality. Sensitivity, that is the ability to correctly identify subjects with endoleaks, was 82% for ultrasonography without contrast and 94% for ultrasonography with contrast. In regard to specificity, which is the ability to correctly exclude the presence of endoleaks, both types of ultrasound provided good estimates - that is - higher than 93%.
In summary, the review suggests that there is good evidence that contrast-enhanced ultrasonography is helpful for confirming or excluding the presence of endoleak in people who received endovascular aneurysm repair. For every 1000 people having a contrast-enhanced ultrasonography evaluation, only 15 people will have their endoleaks missed and 47 people would need to undergo a CT scan that would prove unnecessary. Therefore, the Cochrane researchers conclude that contrast-enhanced ultrasonography can be introduced as a routine diagnostic modality for an endoleak surveillance programme, followed by CT scan if the ultrasound is positive so that the type of endoleak and its subsequent management can be established.

John: If you would like to look in more detail at the evidence in this Cochrane Diagnostic Test Accuracy review, visit the Cochrane Library online at Cochrane Library dot com, where you can find the review with a simple search for 'ultrasonography for endoleak detection'.