How Dialysis Works Dialysis acts as an artificial kidney. About 90 percent of dialysis patients receive hemodialysis, in which the blood is circulated outside the body and cleaned inside a machine before returning to the patient. Before hemodialysis can be done, a doctor must make an entrance, called an access, into the patient's blood vessels. This is done by minor surgery in the leg, arm or sometimes neck. The best access for most patients is called a fistula.
Minor surgery is performed to join an artery to a vein under the skin to make a larger vessel.
If no vessels are suitable for a fistula, the doctor might use a soft plastic tube called a vascular graft to join an artery and vein under the skin. For temporary dialysis in the hospital, a patient might need a catheter implanted into a large vein in the neck. Once the access is made and healed, two needles are inserted in the fistula or graft, one on the artery side and one on the vein side. Blood drains into the dialysis machine to be cleaned. The machine has two parts, one side for blood and one for a fluid called dialysate.