Plasmapheresis

Plasmapheresis, or plasma exchange, is a treatment for certain diseases.  

Superficially it looks like haemodialyisis because it involves a machine similar to a haemodialyser but in the case of plasmapheresis, all of the plasma (the liquid component of the blood) is filtered and either replaced with an albumin (protein) solution or returned to the body after a certain fraction has been removed.