What does a type 2 endoleak represent?

A type 2 endoleak occurs when there is retrograde blood flow from a branch vessel into the aneurysm sac. This is typically due to collateral circulation, which can occur if blood vessels such as the inferior mesenteric artery or lumbar arteries are supplying the aneurysm sac after the endovascular aneurysm repair (EVAR) procedure. This means that even though the primary structure designed to contain the blood flow has been placed, blood can still enter the aneurysmal sac from adjacent vessels, leading to a type 2 classification.

In contrast, device-related leaks are associated with mechanical failures of the stent-graft, such as gaps between the graft and the vessel wall, and would not be classified as a type 2 endoleak. Type I endoleaks occur at the graft attachment sites where there is incomplete sealing, while type III endoleaks arise from disconnects or defects within the graft materials themselves. All these options represent different types of endoleaks that are not consistent with the definition of a type 2 endoleak.