In all humans, the blood carries many impurities which have to be removed and disposed of. The major waste product is urea, which is filtered through the kidneys to produce urine, which is then passed out of the body. Under normal circumstances the majority of the impurities are removed by the kidneys.
The human kidney is susceptible to infection in various ways. Often bacteria can move from other parts of the body, especially the bladder, to the kidneys. Throat infections can also lead to kidney infections. When the kidney becomes infected, the damage can prevent it from being able to purify the blood. Should the kidney fail completely, its duties must be carried out by an artificial kidney, known as the dialysis machine.
Now a common machine in most hospitals, it was invented in Holland in the 1940's by Willem Kolff. The blood is diverted through a link in the arm or leg, known as a shunt, into the dialysis machine. Here it is passed over the large surface area of a membrane, the impurities soaking through the membrane forming a waste liquid in a container on the other side.
The process takes a few hours to complete, and a patient with kidney failure would need to go into hospital normally two or three times a week for dialysis. It is, however, only a stop gap measure as it does not cure the kidneys. The normal conclusion if the failure is irreversible is to continue with dialysis until a replacement kidney becomes available. A transplant is then carried out, with the intention that the patient can then lead a normal life.
