Arteriovenous Fistula (AVF)
Arteriovenous shunts (whether fistula or graft) are all completely underneath the skin; nothing sticks out from the skin. To do dialysis, two needles are placed through the skin into the access and the needles are connected to the dialysis machine via long plastic tubing. Just like with a dialysis catheter, one needle takes blood out of the body, and the other returns blood after it has run through the dialysis machine.
To make an arteriovenous fistula (AVF), the vascular surgeon connects a vein directly to a nearby artery. This is almost always done in the arm. Arteries are high-pressure blood vessels that deliver blood from your heart to the rest of the body. Veins are low-pressure blood vessels that return blood in the opposite direction, from the body back to the heart. By sewing a vein and an artery together, the vein is exposed to the higher pressure of the artery, which makes the blood flow much faster through the vein. This helps the vein to get a little bigger and the wall of the vein a little thicker so that it can then work with the dialysis machine.
Most fistulas are made through a small incision in the upper arm or the forearm. The operation is an outpatient procedure and generally takes less than an hour. Before it can be used for dialysis, an AVF must grow enough to handle the dialysis needles. This can take two to three months or more; for this reason, it is recommended to have the AVF surgery done at least several months before dialysis is needed. If the fistula is not making progress, a wire-based procedure may be required using a balloon to stretch the vein and help it get bigger (angioplasty).
The best long-term dialysis access is an arteriovenous fistula because it uses all-natural tissue and therefore can last longer and is more resistant to infection and clotting. However, this requires that the patient have a good arm vein to use for the fistula. This can be determined by an ultrasound of the veins (vein mapping) before surgery to look at the size of the veins, and any sign of damage from previous blood draws or IV catheters.