[Urea kinetic model analysis in dialysis: from theory to practice].

Urea kinetic modeling (UKM) has been originally proposed by F. Gotch and J. Sargent as a guide to optimize and individualize the dialysis prescription in uremic patients. In a recent report, the US National Cooperative Dialysis Study group, showed the power of this approach compared to conventional methods. It was also concluded that dialysis adequacy could be predicted with a high success rate by determining three parameters; uremia represented by the Urea Time Averaged Concentration, dialysis dose defined as KT/V ratio, and dietary protein intake calculated from the urea generation rate. In spite of its potential usefulness, UKM has not gained clinical acceptance among nephrologists since it appeared always complicated due to its mathematical formulation or cumbersome to be used routinely in dialyzed patients. In this paper the authors will bring the reader from basic concepts to practical use of UKM to guide dialysis strategy. Limits of validity and difficulty in using this approach are also discussed. It is concluded that UKM by using very simple and basic parameters is a practical, and very powerful tool for assessing the dialysis adequacy and nutritional status of dialyzed patients. Direct quantification from dialysate (or ultrafiltrate) collection appeared a simple and precise method which should avoided multiple blood sampling.