Kidney dialysis. View of a man reading a book as he undergoes kidney dialysis (haemodialysis). Two tubes are visible at upper centre which connect the patient to the dialyser (artificial kidney) at upper right. Dialysis is necessary for people whose kidneys do not function properly; it is used to remove waste material from the blood. Blood is pumped out of the patient through one of the tubes into the dialyser. There the blood undergoes fine filtration to remove the waste material. The clean blood is then pumped back into the patient through the other tube.