Dialysis is a process of separating dissolved substances from a solution using a semi-permeable membrane which allows only some dissolved substances to pass through. Many substances such as cell walls and cellophane act as semi-permeable membranes.
Dialysis is used to remove waste-products from the blood of patients with impaired kidney function. Accumulation of waste products especially urea, in the blood can prove fatal.
Dialysis of blood is carried out using a dialysis machine. Blood drawn from the artery in the forearm of the patient is passed through a semi-permeable membrane. The tubing is placed in a solution called dialysis fluid. Since the blood has a high concentration of impurities compared to the dialysis fluid, a concentration gradient builds up. This results in a flow of soluble impurities from the blood into the dialysis fluid. This continues till the concentrations on each side of the membrane are balanced. To prevent clotting of blood in the dialysis machine, the anti-clotting substance heparin is used.
Although usually done in a hospital, home dialysis is possible today. A patient can even carry a portable dialysis machine which allows freedom of movement. Dialysis is usually a second choice to a kidney transplant and is used only until a suitable donor kidney becomes available.
