How peritoneal dialysis works

In peritoneal dialysis (as in Haemodialysis), wastes are removed from the blood by a process called diffusion.

Excess water is removed from the blood in peritoneal dialysis by a process called osmosis, illustrated here. A substance (usually glucose) is put into the dialysis fluid which pulls the water from the blood.

A thin layer of natural tissue (the peritoneal membrane), keeps the blood apart from the dialysis solution (also called the dialysis fluid, or the dialysate).
Blood cells are too big to pass through the semi-permeable membrane, but water in the blood is drawn into the dialysis fluid by the glucose.
Ultrafiltration is complete. Water has been drawn through the peritoneum by the glucose in the dialysis fluid. There is now extra water in the dialysis fluid, which needs to be changed.

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May 1, 2006

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