 Chronic Kidney Disease CKD is a long-term condition in which the function of the kidneys - to filter out waste products from the blood - slowly declines. When renal function becomes sufficiently low it is described as End Stage Renal Disease ESRD and renal replacement therapy RRT is likely to be needed to prolong life. The most common type of RRT is haemodialysis, in which the patients blood is filtered through a machine. 