Historical milestones of a long pathway.

Hemodiafiltration (HDF), developed from the combination of hemodialysis and hemofiltration, is considered to be the most effective current procedure to remove uremic toxins from the blood of kidney patients. Historically, the clinical use of HDF was for many years limited due to the cost burden related to the large amount of sterile volume replacement fluid needed. The solution offered was on-line preparation of replacement fluid from standard dialysate by means of membrane filtration. Industry opened to this concept quite early and worked on various technical solutions between the early 1980s and the late 1990s before real state-of-the-art systems became commercially available on a broad basis. This article reviews in particular the activities of initially Fresenius and later Fresenius Medical Care in this field and identifies major concepts and prototypes up to today's commercially available high-end product--the 5008 therapy system--where on-line HDF finally became integrated as a standard component.