Solute Transport in Hemodialysis: Advances and Limitations of Current Membrane Technology

Extracorporeal therapy for end-stage renal disease is now provided to more than three million patients globally. Nearly all treatments are performed with filters containing hollow fiber membranes, removing solutes and water by diffusion, convection, and ultrafiltration. In this review, we will provide a detailed quantitative analysis of the transport processes involved in different hemodialysis (HD) therapies. We will also report some technical aspects of hollow fiber membranes and filters composed of them along with the mechanisms of solute and water removal for such devices. Diffusive mass transfer will be assessed according to the three major aspects of a hollow fiber filter (blood compartment, membrane, and dialysate compartment). With regard to convective transport, the importance of internal filtration as a solute removal mechanism in high-flux HD will be highlighted, along with the critical role that blood/membrane interactions assume in filtration-based therapies.