Mr Gibbs explains that an endoleak is the finding of blood flowing into the aneurysm around a stent graft (medical device) after it has been inserted in endovascular (keyhole) repair. This is one of the important complications to be aware of and can be found on scans during follow up. There are different types of endoleaks, some of which can lead to high pressure blood flow into the aneurysm, and these need procedures to prevent rupture (bursting).