Procedure for Haemodialysis: When the kidneys are completely damaged and do not function, the patient often receives haemodialysis (treatment with an artificial kidney). Haemodialysis is the separation of certain substances from blood by use of a selectively permeable membrane.

The pores in the membrane allow some substances to pass through, however, prevent others. The patient is connected to the machine by a tube attached to an artery often the radial artery.

Blood from the artery is pumped into a tube that runs through the dialyzer. The dialyzer is filled with dialysis fluid which contains the same quantities of electolytes and nutrients as normal plasma but contains no waste products. The cellophane tube (a tube bounded by thin membrane) is kept in the dialysis fluid. The pores in the cellophane tube tube do not allow the movement of blood cells and proteins from the blood into the dialysis fluid, but are large enough to allow smaller molecules to diffuse into the fluid. Molecules of waste substances such as urea, ammonia and waste diffuse into the dialysis fluid. Diffusiion of other substances such as glucose, amino acids and electrolytes is prevented by the presence of these substances in the dialysis fluid in the same concentration as in the normal plasma. Now the blood is returned to the patient body through a vein usually the radial vein.