Dialysis is a physical process used by chemists to separate multiple dissolved substances from a solution using the principle of “osmosis”, i.e. diffusion through a “semi-permeable membrane”. It was discovered by the Scottish scientist Thomas Graham in 1854 and successfully applied in patients with kidney failure in 1943.

The early cellophane-based devices used for ‘hemodialysis”, have been progressively improved leading to the currently used “filters”, composed of thousands of very thin hollow tubes of synthetic petroleum products. The patient’s blood is pushed inside these tubes by a special pump, and is prevented from clotting by a thinning substance. A clean fluid, with a composition similar to that of normal body fluids, circulates outside the tubes. Wastes and excess water diffuse out of the blood through the capillary walls and are thrown away.

Another modality of dialysis treatment uses the peritoneum, the membrane that normally covers abdominal organs, to take the role of the synthetic petroleum membrane used in hemodialysis. Blood circulates in the normal capillaries of the peritoneal membrane and therefore does not need any thinning. The ‘washing fluid” is introduced into the abdominal cavity by a special plastic tube, remains for a variable time and drained away with the wastes extracted from the patient’s blood.