Hemodialysis is a procedure where a dialysis machine and a special filter called an artificial kidney, or a dialyzer, are used to clean your blood. To get your blood into the dialyzer, the doctor needs to make an access, or entrance, into your blood vessels.  Artificial kidneys contain a number of tubes having a semi-permeable lining, suspended in a tank filled with dialysing fluid.This fluid has the same osmotic pressure as that  of blood except that it is devoid of nitrogenous wastes.The patient’s blood is passed through these tubes.During this passage, the waste products from the blood passes into dialysing fluid by diffusion.The purified blood is pumped back into the patient.