Dialysis is the artificial process of getting rid of waste (diffusion) and unwanted water (ultrafiltration) from the blood. This process is naturally done by our kidneys. Some people, however, may have failed or damaged kidneys which cannot carry out the function properly – they may need dialysis. In other words, dialysis is the artificial replacement for lost kidney function (renal replacement therapy). Dialysis may be used for people who have become ill and have acute kidney failure (temporary loss of kidney function), or for fairly stable patients who have permanently lost kidney function (stage 5 chronic kidney disease).