We read with great interest the recent study by Zoccali and colleagues regarding the association between long term fluid volume fluctuations and mortality in patients with kidney failure [1]. The authors present a compelling analysis of the NephroCare cohort, sublimating the traditional nephrological focus from static volume overload to the dynamic instability of hydration status. While the identification of fluid variability as an independent prognostic marker is a seminal contribution, several critical issues warrant further discussion.
