Dialysis is a procedure that cleans and filters the blood when the kidneys are not working properly in their role of removing wastes and fluid from the body.
Who is a candidate for the procedure?
Dialysis is used to treat people with kidney failure, which can be either acute renal failure (is usually reversible and dialysis is only temporary) or chronic renal failure (called ESRD or End Stage Renal Disease which is not reversible).
Treatment is needed to replace the work of the failed kidneys. Once both kidneys fail, a person would die as a result of not having the filtering process normally supplied by the kidneys .
Dialysis is way to keep a person with kidney failure alive. A person waiting for a kidney transplant also would be a candidate for dialysis.
How is the procedure performed?
There are two main ways to filter the blood:
- In hemodialysis, blood is filtered using a special dialysis machine and an artificial kidney. Blood removed from the body travels through tubes into the dialysis machine. The machine has a special, custom made filter or artificial kidney that filters out wastes and extra fluids by diffusion, osmosis, and convection.
The machine can be adjusted to remove exactly the amount of fluid that is necessary. Fluid and medicine can also be given on dialysis. The newly cleaned blood flows through another set of tubes and back into the body.
Ideally only wastes and fluids are removed, no blood cells are lost.
- In peritoneal dialysis, a special tube is put into the abdomen through the skin. A cleansing solution called dialysate travels through the tube into the abdomen.
The peritoneum (the lining around the entire abdomen inside including all the intestines) has as much area as a person's skin surface and lots of blood vessels to exchange materials.
After several hours, the fluid gets drained from the abdomen. It takes wastes from the blood with it by diffusion, osmosis, and convection. This process may be repeated several times a day. Or it can be done during the night while the person sleeps by a machine.
Both types of dialysis require surgery to prepare the person's body:
- For hemodialysis, a surgeon will create a new access to the bloodstream called a fistula. This provides a way for blood to be carried from the body to the dialysis machine at a brisk rate (200cc/min or faster). The access may be either inside the body, usually in the arm, or outside the body, usually in the neck.
- For peritoneal dialysis, a surgeon places a small, soft tube called a catheter into the abdomen. This tube stays in place.