In medicine, dialysis (from Greek διάλυσις, diàlysis, "dissolution"; from διά, dià, "through", and λύσις, lỳsis, "loosening or splitting") is the process of removing excess water, solutes and toxins from the blood in those whose native kidneys have lost the ability to perform these functions in a natural way. This is referred to as renal replacement therapy.
Dialysis may be used in those with rapidly developing loss of kidney function, called acute kidney injury (previously called acute renal failure); or slowly worsening kidney function, called Stage 5 chronic kidney disease, (previously called chronic kidney failure and end-stage renal disease and end-stage kidney disease).
Dialysis is used as a temporary measure in either acute kidney injury or in those awaiting kidney transplant and as a permanent measure in those for whom a transplant is not indicated or not possible.
In the United Kingdom and the United States, dialysis is paid for by the government for those that are eligible. The first successful dialysis was performed in 1943.
In research laboratories, dialysis technique can also be used to separate molecules based on their size. Additionally, it can be used to balance buffer between sample and the solution "dialysis bath" or "dialysate" that the sample is in. For dialysis in a laboratory semipermeable membrane is used as a tube made of cellulose acetate or nitrocellulose where pore size can vary according to the size separation required. Control over pore size allows a better separation between small molecules while leaving large molecules of interest inside. Solvents, ions diffuse easily through the pores while leaving the big molecules behind and separate. In protein purification technique dialysis is used to exchange buffers, loose smaller proteins that can pass through the pores, dilutions of concentrated salts, while leaving the protein of interest inside the semipermeable membrane separated.