In order to appreciate how this will work, it may be useful to have an overview of natural kidney function. The kidney does its work of cleansing the blood in two steps. First, the blood is grossly filtered by driving the blood through a structure consisting of a tangled wad of capillaries. Under stepped-up pressure, small molecules are driven out through the capillaries leaky walls. A great deal of water and other valuable small molecules are also filtered out in the process.
Current technology reproduces only the first step.
The artificial kidney now used in dialysis is comprised of thousands of fine hollow fibers with porous walls. The patient s blood, laden with metabolic wastes, is diverted through the fibers. These are bathed in a fluid that draws off waste molecules. Typically, a blood-cleansing session lasts about three hours and must be repeated three times each week throughout the life of the individual. Though a life-saving technology, dialysis clearly places an enormous burden on the patient.