Endoleak Type II is diagnosed by detecting retrograde flow into the aneurysm sac from which sources?

• A. Visceral arteries
• B. Branch vessels such as lumbar and inferior mesenteric arteries
• C. Renal arteries
• D. Celiac trunk

Answer: (B)

Type II endoleaks arise when blood continues to flow retrograde into the aneurysm sac from collateral branches that originate from the aorta outside the graft. The most common sources are the lumbar arteries and the inferior mesenteric artery, which can remain patent and send blood back into the sac after EVAR. This retrograde filling keeps the sac pressurized and detectable on imaging.

Renal arteries and the celiac trunk are not the usual feeders for this mechanism; they are major visceral branches that don’t typically provide the backflow into the aneurysm sac seen with Type II endoleaks. Thus, the classic sources to look for are branch vessels like the lumbar arteries and the inferior mesenteric artery.