Dialysis is the process by which toxins and metabolic waste products are removed from the human body as a form a therapy in patients with kidney disease. The procedure is considered organ replacement therapy in that the function of an organ (the kidney) is being replaced by a machine. However no machine is capable of adequately replacing the diverse and complex functions of the kidney. Dialysis therefore is a continuously evolving process forever attempting to achieve the unattainable perfection of full organ replacement.
There are two main forms of dialysis, haemodialysis and peritoneal dialysis. The two forms differ greatly in how they achieve the same result. While neither one is inferior to the other the older and more common modality is haemodialysis.
Haemodialysis is performed by passing blood through a circuit of tubings across a dialyser membrane which functions as a microscopic seive which preserves vitally important constituents of blood while filtering out the toxic breakdown products of daily metabolism. As blood is removed so is it continually returned to the patient so that only a small fraction of the blood is outside of the body at any one time. The procedure usually averages 4 hours and patients are free to continue a near normal life with a few restrictions in between sessions which are generally scheduled three times per week.
Peritoneal dialysis on the other hand does not involve the use artificial filtration membranes or removal of blood. Every human is born with what is known as a peritoneal membrane a one cell thick lining which covers the internal organs within the abdomen. This lining is richly supplied by blood vessels. The peritoneal dialysis procedure makes use of this by infusing fluid into the peritoneal cavity. The fluid infused is sterile, free of bacteria and toxins. Because the peritoneal lining is only a single cell thick and richly supplied by blood vessels any toxins present within the blood will slowly leech through the peritoneal membrane and into the fluid that was placed in the abdomen. After a period of time has elapsed the fluid becomes filled with toxins that have been removed from the body. The fluid can then be drained out of the abdomen and fresh fluid replaced to continue the process of dialysis. The procedure generally takes longer than haemodialysis but the patient is ambulant during that time and not confined to a dialysis chair. Patients are taught the sterile technique of self dialysis and may even perform the procedure while at work at school or on vacation at a resort. With peritoneal dialysis you take your dialysis unit with you.
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