Surgical connection of an artery directly to a vein, usually in the forearm, created in people who will need hemodialysis. The AV fistula causes the vein to grow thicker, allowing the repeated needle insertions required for hemodialysis. Development of the AV fistula takes 4 to 6 months after surgery before it can be used for hemodialysis. The AV fistula is the preferred method of access. See hemodialysis under dialysis.