Like hemodialysis, peritoneal dialysis removes toxins from the blood of a patient with acute or chronic renal failure. But unlike hemodialysis, it uses the patient’s peritoneal membrane as a semipermeable dialyzing membrane. In this technique, a hypertonic dialyzing solution is instilled through a catheter inserted into the peritoneal cavity. (See Catheters for peritoneal dialysis.) Diffusion allows excessive concentrations of electrolytes and uremic toxins in the blood to move across the peritoneal membrane and into the dialysis solution. Excessive water in the blood moves across the peritoneal membrane by osmosis. After an appropriate dwelling time, the dialysis solution is drained, taking toxins and wastes with it.

Peritoneal dialysis may be performed by an automatic cycler machine or as continuous ambulatory peritoneal dialysis (CAPD). The cycler machine requires sterile set-up and connection technique.

Because the patient himself performs CAPD, the method causes minimal disruption to the patient’s life by allowing him to remain active during dialysis. In CAPD, the patient uses a peritoneal catheter to instill dialysis solution into his peritoneal cavity. After the solution is instilled, the patient can attach a sterile cap to the catheter end and proceed with his normal activities as the solution remains in the peritoneal cavity. After 4 to 6 hours of dwelling time, the patient reconnects the peritoneal catheter to sterile tubing, allows the fluid to drain via gravity, and instills fresh dialysis solution. He repeats the process to ensure continuous dialysis 24 hours per day, 7 days per week.