# 93 Dialysis and its application in kidney machines
The usual treatment for a person with kidney failure is to have several sessions a week using a dialysis unit (a kidney machine), to maintain the glucose and protein concentration in blood diffusion of urea from blood to dialysis fluid.
Dialysis is a method of removing one or more components from a solution using the process of diffusion. The solution is separated from a bathing liquid contains none of the components that need to be removed from the solution, so these pass from the solution, through the membrane, into the bathing dilution by diffusion. The bathing solution needs to be changed regularly to maintain a concentration gradient.
A patient with kidney failure needs to have toxic chemicals removed from the blood to stay alive. Blood is removed from a vein in the arm, and is kept moving through dialysis tubing in the dialysis machine using a pump. The tubing is very long to provide a large surface area. The dialysis fluid has a composition similar to blood plasma, but with no urea or uric acid. Urea or uric acid and excess mineral salts are removed from the blood, by diffusion, into the dialysis fluid. The cleaned blood is then passed through a bubble trap to remove any air bubbles, before being returned to the patient’s vein.
Advantages and disadvantages of kidney transplants compared with dialysis.
Advantages
Disadvantages
Video: Hemodialysis and how it works
Advantages
- The patients can return to a normal lifestyle – dialysis may require a lengthy session in hospital, 3 times a week, leaving the patient very tired after each session.
- A dialysis machine will be available for other patients to use.
- Dialysis machines are expensive to buy and maintain.
Disadvantages
- Transplants require a suitable donor – with a good tissue match. The donor may be a dead person, or a close living relative who is prepared to donate a healthy kidney (we can survive with one kidney_.
- The operation is very expensive.
- There is a risk of rejection of the donate kidney – immunosuppressive drugs have to be used.
- Transplantation is not accepted by some religions.
Video: Hemodialysis and how it works