Evolution of hemodiafiltration.

The evolution of hemodiafiltration (HDF) has become possible by the advances in the construction of dialysis membranes. The availability of a high-flux membrane, partially hydrophilic with high sieving coefficients and a reduced wall thickness has made it possible to conveniently combine diffusion and convection for blood purification. The second important step has been the development of accurate ultrafiltration control systems. Machines capable of managing large amounts of fluid turnover allowed safe and effective HDF. Some new dialysis machines are specifically designed to perform HDF with adequate embedded software. The third step regards the production of large amounts of ultrapure dialysate and replacement fluid. For years replacement fluid was produced in bags, while recently, online production has enabled high volume exchanges in HDF. All these advances, together with the creativity of several groups, have spurred new interest in HDF and have led to the development of various HDF techniques, which are successfully applied to uremic patients with important clinical benefits.