Ultrapure dialysis fluid--how pure is it and do we need it?

Originally a definition of water quality for the semiconductor industry, the term ‘ultrapure’ has been adopted by the dialysis community. The discussion has developed from basic definitions and methods for quantification to clinical benefits and recommendations for implementation. Today, ultrapure dialysis fluid is subject to the demands of evidence-based medicine or at least evidence-based cost-effectiveness. The sequence from growing awareness to widespread conviction and practical implementation of ultrapure dialysis fluid is similar to the process for biocompatible dialysis membranes some 10–15 years ago. So, where do we stand with regard to ultrapure dialysis fluid?