How does peritoneal dialysis work?
Peritoneal dialysis is a means of removing waste (such as urea, creatinine, and phosphate), other solutes (i.e., sodium and chloride), and excess fluid from the body when the kidneys have failed.
A sterile solution (PD fluid) containing a balanced concentration of electrolytes and an osmotically active agent is introduced into the patient’s peritoneal cavity by a PD catheter or tube.
The latter is placed surgically (laparoscopic or open) or by interventional (bedside or radiologic) technique. The introduced PD fluid bathes the expansive network of capillaries covering the surface area of the peritoneum. As the PD fluid is devoid of any waste, solutes move down concentration gradients across peritoneal capillaries into the PD fluid over time until near-equilibrium of uremic solute concentrations is reached between the blood and the PD fluid. Once this occurs, the PD fluid (“dialysate effluent”) is drained, again through the PD catheter. The process is then repeated with fresh PD fluid. The osmotically active agent present in the PD fluid draws fluid, called ultrafiltrate, across the peritoneal capillaries into the PD fluid. Wastes and excess fluid are removed when “spent” PD fluid effluent is drained. The cycle of infusion of PD fluid, followed by its dwell in the peritoneum, and subsequent drainage from the patient is referred to as an “exchange.”