An arterovenous aneurysm in which the blood is carried into the vein through a connecting pulsating sac.

The associated veins also may be dilated and pulsating.

An aneurysm is a localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture.

The word aneurysm comes from the Greek aneurysma meaning "a widening".