Urea and Uremic Solutes: How Does Peritoneal Dialysis Work?

The transport of urea and other solutes across the peritoneal membrane follows the general dialytic principles of diffusion and convection. Nevertheless, the unique anatomic configuration of the peritoneum suggests that specific modeling is needed to explain solute kinetics in peritoneal dialysis. The historical two-pore model of membrane transport had to be adjusted by adding a third pore, and the distributed model has further complemented this analysis. Recent findings with regard to the endothelial glycocalyx add an additional level of complexity. Unfortunately, most studies to date use only urea, glucose, and creatinine kinetics to describe transport during peritoneal dialysis and adequacy of solute removal. Studies of transport of other classes of uremic solutes are scanty but allow us to gain insight into how peritoneal dialysis works.