MODEL RELEASED. Kidney dialysis. Patient undergoing haemodialysis treatment. A tube carries blood from a blood vessel his forearm to a dialysis machine (upper right). This acts as an 'artificial kidney' to remove waste products and excess fluid from the blood. The filtered blood is then returned through a second tube into the patient's body. This cleaning of the blood is usually done by the kidneys. If they are damaged, waste products build up in the blood, which can be fatal. Haemodialysis takes between 2 and 6 hours and must be carried out several times a week.