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

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

Answer: (A)

Incomplete deployment creates a poor seal at the ends of the stent graft, allowing blood to continue flowing into the aneurysm sac around the graft. This high-pressure leakage at the proximal or distal attachment is a Type I endoleak, defined by seal/attachment failure at the graft ends. Because the leak keeps pressurizing the aneurysm sac, it carries a high rupture risk and typically requires urgent correction to reestablish a complete seal (such as repositioning the graft or adding cuffs).

By contrast, Type II endoleaks come from retrograde flow through branch vessels into the sac and are not due to a failed graft seal. Type III endoleaks arise from defects in the graft material or disconnection between components. Type IV endoleaks result from graft porosity and are usually transient with modern devices.