Is an av fistula permanent or temporary?

Depends: If this is an aquifers avf from catheterization or other vascular injury it should be repaired and is temporary. If you are referring to a avf for dialysis this is relatively permanent.

Both?: We place av fistulas hoping for long term durability. That being said, we close av fistulas all the time, for complications, for failure, or (most importantly) after renal transplant.

Permanent w/o repair: An AV fistula, or arterial-venous fistula, is an abnormal connection between an artery & vein that allows high pressure arterial blood to travel into the low pressure venous system. It can be caused by traumatic blood vessel injury or purposely created surgically by a doctor (e.g for dialysis access). An AV fistula is always permanent unless repaired surgically or with covered stenting of vessels.