In a very small number of people there is complete failure of both kidneys. Ten years ago, this would have meant certain death. Nowadays, they can be kept well by a very rigorous diet, by dialysis - purifying their blood two or three times a week -or by transplanting a kidney.
What is it like to use an artificial kidney machine as a vital part of your life?
In tonight's programme, people involved in dialysis and kidney transplantation discuss some of the problems which they have to overcome, in hospital or at home.