The word dialysis (the separation of soluble substances from colloids and their removal through a semipermeable membrane down a concentration gradient) was coined by Thomas Graham in 1861, in Glasgow, Scotland. It was not, however, until the first success with dialysis in kidney failure, by Kolff in Kampen, Holland, in 1945, and the invention, in Seattle, WA, in 1960, of the Scribner shunt for access to the circulation that modern hemodialysis as we know it became practical. Both Kolff and Scribner received the Albert Lasker Award for Clinical Medical Research in 2002 for their breakthrough concepts. Currently, more than 1 million patients worldwide undergo either hemodialysis (the vast majority) or peritoneal dialysis to maintain life(1). During dialysis, small molecules are removed by the process of diffusion, but removal of larger molecules is dependent on convective transport, which necessitates ultrafiltration to improve “solvent drag” of larger substances along with the ultrafiltered fluid(2). Traditional uremic toxins, such as urea, creatinine, sodium, potassium, and water, were the early focus of nephrologists, but it became clear that other larger molecules, theoretically “middle molecules” around 1.5 kDa, were as important in promoting morbidity if the patient was not dialyzed for a protracted period(2). The middle molecule hypothesis was popular in the 1970s but has been largely superseded by the demonstration that even larger molecules, the low–molecular-mass proteins from 5 to …