On-line hemodiafiltration therapy for end-stage kidney disease patients: Promises for the future? What's next?

On-line hemodiafiltration (OL-HDF) is currently the most advanced form of blood purification modality leading convective-based therapies in end-stage kidney disease patients. By adding a high convective component to the diffusive clearance achieved with highly permeable dialyzers, OL-HDF reinforces removal of small MWt compounds and enlarges the spectrum of uremic compounds cleared up to middle and large MWt compounds. The biological and clinical benefits of convective-based therapy are currently also being explored in a revisited hybrid modality, combining an increased internal filtration process with a more open membrane. Regular use of ultrapure dialysis fluid required by convective-based therapies improves the bio-incompatibility of the extracorporeal circuit so reducing inflammatory responses. On-line production of substitution fluid, relying on a cold sterilization by ultrafiltration, has several advantages: First, it is a safe and established process; and second, it provides an unlimited amount of substitution fluid at the same cost as regular ultrapure dialysis fluid. As such, OL-HDF is adaptable to all substitution modalities (post, pre, or mixed-HDF), thus allowing the dialytic convective dose to be adjusted to the individual patient needs. The development of OL-HDF opens new pathways such as task automation simplifying care workflow. All these features make OL-HDF the most versatile dialysis modality that can be now integrated in various treatment schedules according to session time and frequency (daily, nocturnal, or alternate day) or location (incenter, satellite, or potentially home-based therapy).