In this pro-con debate, we will analyse the relevance of data supporting the prime role of uraemic toxins versus salt and volume overload as the main driver for the impressive mortality and morbidity characteristic of any end-stage renal disease patient.

Firstly, we are going to review the circumstantial evidence and associated studies/clinical observational data which only weakly suggest that uraemic solutes are indeed linked to damage to the body and its constituents, especially the cardiovascular (CV) system. At the same time, we will equally thoroughly discuss the ‘fact’ that decreasing salt and fluid load is essential for any dialysed patient. Evidence in favour of a prominent role for uraemic toxins is appealing from a pathophysiological point of view, but unfortunately is misleading in real life practice. Evidence in favour of salt and water reduction is overwhelmingly stronger.

This difference in apparent evidence strength notwithstanding the weaker support for uraemic toxins does not take away from clinical importance of minimizing uraemic toxicity load in the large majority of the dialysis population.

The uraemic syndrome is characterized by the accumulation of toxic compounds that are normally secreted into the urine by healthy kidneys. These compounds are classified according to their molecular weight and protein-binding ability and, in some studies, have repeatedly been associated with inflammation, oxidative stress, vascular calcification, endothelial damage, and recently, with an increased overall and CV mortality risk [1].

If the hypothesis of a primary role for uraemic toxins holds true, then the obligatory corollary should also be true: better survival/clear improvement in outcomes when any form of ‘better dialysis’/‘better removal’ is applied. Unfortunately, the accumulating evidence does not strongly support this hypothesis. Better dialysis/better removal, which may theoretically and practically be achieved by high-flux dialysis, haemodiafiltration (HDF) or more frequent/longer dialysis, was only partially associated with …

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