MODEL RELEASED. Female patient using a kidney machine to undergo renal dialysis. A kidney machine replaces the function of the kidneys in removing waste materials from the bloodstream. A stream of blood from an artery is circulated through the machine on one side of a semi- permeable membrane, while a solution of comparable electrolytic concentration circulates on the other side. Water & waste products pass across the membrane but blood cells & proteins are too large to do so. Purified blood is returned to the patient through a vein.