Kidney dialysis. Nurse comforts an elderly woman during the procedure of kidney dialysis (haemodialysis). Tubing can be seen leading to the patient's arm from the artificial kidney machine at centre. In haemodialysis, one tube passes blood out of the patient where it is run through an artificial kidney machine to remove waste products from the blood. The cleansed blood is then returned to the patient through the other tube. Haemodialysis is necessary when the kidneys fail to remove waste and excess water from the blood. The procedure takes 2-6 hours and is usually carried out many times a week. An alternative to dialysis is a kidney transplant.