Dialysis

Dialysis is a mechanical process that performs the work of healthy kidneys. In a clinical context Dialysis is a method for removing waste such as urea from the blood when the kidneys can no longer do the job.

Before dialysis can begin, the doctor has to create a dialysis access. In hemodialysis, the access is the place where the dialysis needles are inserted, to carry the blood to and from the dialysis machine. For the best access, the doctor builds a connection, called a fistula, between an artery and a vein in the forearm. Or the doctor uses a tube called a graft to connect the artery and a vein. Sometimes a plastic tube (central venous catheter) is placed in the neck.

The two types of dialysis are: hemodialysis and peritoneal dialysis.

Hemodialysis and peritoneal dialysis may be used to treat people with diabetes who have kidney failure. It works by having the blood flow along one side of a semi-permeable membrane, with the dialysis solution (usually a highly concentrated saline) flowing along the other side. Due to the difference in osmolarity between the two liquids, water traverses the membrane in order to dilute the dialysis liquid, carrying along the unwanted blood contents.

Hemodialysis

Hemodialysis uses a man-made membrane (dialyzer) to remove wastes and extra fluid from the blood. It also restores the proper balance of certain minerals in the blood (electrolytes). The fluid used to filter or clean the blood is called dialysate. Hemodialysis is usually done in a hospital or dialysis center.
In hemodialysis, the patient's blood is passed through a tube into a machine that filters out waste products. The cleansed blood is then returned to the body.

Peritoneal dialysis

In peritoneal dialysis, a special solution is run through a tube into the peritoneum, a thin tissue that lines the cavity of the abdomen. The body's waste products are removed through the tube.

There are three types of peritoneal dialysis:

• Continuous ambulatory peritoneal dialysis (CAPD), the most common type, needs no machine and can be done at home.
• Continuous cyclic peritoneal dialysis (CCPD) uses a machine and is usually performed at night when the person is sleeping.
• Intermittent peritoneal dialysis (IPD) uses the same type of machine as CCPD, but is usually done in the hospital because treatment takes longer.

External links:
http://www.doctorslounge.com/nephrology/procedures/dialysis.htm
http://myhealth.ucsd.edu/library/healthguide/en-us/support/topic.asp?hwid=zm2610
http://www.renalpatients.co.uk/capd.htm