An<unk>  is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm.
Arteriovenous fistula
Dural ectasia
Dural arteriovenous fistula
Pseudoaneurysm
Developmental venous anomaly
Arterial insufficiency ulcer
Tuberculous gumma
Arteriovenous nicking