Incomplete stent deployment during endovascular aneurysm repair is most likely to cause which endoleak type?

• A. Type I
• B. Type II
• C. Type III
• D. Type IV

Answer: (A)

Endoleak types are defined by how the leak occurs. If the stent graft doesn’t deploy fully, it can’t seal tightly at its attachment points to the aorta or iliac arteries. That gap lets arterial blood pressurize and flow into the aneurysm sac from the ends of the graft, which is exactly what a Type I endoleak is—an leak at the proximal or distal seal due to inadequate apposition.

In contrast, a Type II endoleak comes from retrograde flow through branch vessels into the sac (like lumbar arteries or the inferior mesenteric artery) and isn’t about deployment quality. Type III endoleaks are from graft-related issues such as fabric defect or separation of graft components, not simply incomplete deployment. Type IV leaks are related to graft porosity and are rare with modern devices.

So incomplete deployment most strongly points to a Type I endoleak because the primary problem is a failed seal at the graft’s attachment sites.