On CT angiography of an abdominal aortic aneurysm, an endoleak is seen on delayed phase with contrast within the excluded sac but no direct connection to the graft or patent lumbar arteries. What type of endoleak is this?
- A Type I endoleak — graft attachment zone leak
- B Type II endoleak — retrograde filling from branch vessels ✓
- C Type III endoleak — graft component junction failure
- D Type IV endoleak — graft fabric porosity
Correct answer: B. Type II endoleak — retrograde filling from branch vessels
Explanation
Type II endoleak is the most common type, accounting for 20–25% of all post-EVAR endoleaks. It results from retrograde filling of the excluded aneurysm sac via patent side branches (inferior mesenteric artery, lumbar arteries). On CT, there is contrast enhancement within the sac without visible direct attachment-zone communication. It is usually managed conservatively as many resolve spontaneously, but intervention is needed if the sac grows. Type I is due to inadequate seal at proximal/distal graft fixation zones. Type III results from modular graft separation.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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