Post-EVAR surveillance includes monitoring for endoleaks and sac size changes. Which finding would most strongly suggest a potential endoleak?

• A. Decreasing sac diameter with color flow within sac.
• B. No color Doppler flow in sac and shrinking sac.
• C. Flow within the aneurysm sac on color Doppler with increasing sac size.
• D. Stable sac size with no color flow.

Answer: (C)

The key idea is that endoleaks are about blood continuing to enter and pressurize the aneurysm sac after EVAR. Seeing color flow inside the aneurysm sac means there is intraluminal flow persisting in the sac. When that flow is accompanied by an increasing sac diameter, it shows the sac is being actively pressurized and expanding due to the endoleak. That combination—flow within the sac plus sac enlargement—most strongly indicates an endoleak that could threaten the repair and may require intervention.

If there’s no color flow in the sac and the sac is shrinking or stable, that suggests the absence of a clinically significant endoleak. Flow within the sac with a shrinking sac could occur with a low-flow or resolving endoleak, but the strong indicator of a true, ongoing endoleak is flow inside the sac with sac expansion.