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Dialysis Handout
Technique for removing waste products from the blood suffering chronic or acute kidney
failure. There are two main methods, haemodialysis and peritoneal dialysis.
In haemodialysis, the patient's blood is passed through a pump, where it is separated
from sterile dialysis fluid by a semipermeable membrane. This allows any toxic
substances which have built up in the bloodstream, and which would normally be filtered
out by the kidneys, to diffuse out of the blood into the dialysis fluid. Haemodialysis is
very expensive and usually requires the patient to attend a specialized unit.
Peritoneal dialysis uses one of the body's natural semipermeable membranes for the
same purpose. About two litres of dialysis fluid is slowly instilled into the peritoneal
cavity of the abdomen, and drained out again, over about two hours. During that time
toxins from the blood diffuse into the peritoneal cavity across the peritoneal membrane.
The advantage of peritoneal dialysis is that the patient can remain active while the
dialysis is proceeding. This is known as continuous ambulatory peritoneal dialysis
(CAPD).
In the long term, dialysis is expensive and debilitating, and transplants are now the
treatment of choice for patients in chronic kidney failure.