Substitution-free hemodiafiltration.

Hemodiafiltration (HDF) has been reported to deliver better dialysis outcomes in patients with end-stage renal disease. Technical advances now allow online-based HDF to be used on a clinical basis. However, HDF is being performed at a limited rate because of the requirement of exogenous fluid infusion, which causes safety and cost issues. Therefore, various modifications on HDF strategies have been devised to achieve the HDF without exogenous fluid infusion, which can be achieved by spontaneous fluid reinfusion. In this article, substitution-free HDF strategies are reviewed in detail, with specific attention to technical aspects of the methodology, in vivo and in vitro efficacies, and applicability to clinical use.