[Estimation of total body water from routine urea kinetics]. / La stima dell'acqua corporea totale per la cinetica dell'urea di routine.

ABSTRACT

The comparison of total body water obtained by Watson formula with results of bioelectrical impedance (BIA) shows a fair approximation (Delta% = 1.0 +/- 8.45). However, when compared to other literature formulas the BIA values are higher (8 divided by 23%), and this discrepancy needs further analysis. Urea kinetics was computed using as input data for distribution volume both the Watson anthropometrical and the BIA TBW values the clearance results do not differ significantly (Delta% = 0.74 +/- 8.35). The Kt/V index results are nearly identical (Delta% = 0.12 +/- 1.17), due to a mathematical loop a wrong input of volume induces a comparable error of the clearance result, while their ratio is unchanged. For practical routine to monitoring dialysis adequacy the Watson anthropometrical formula has proven as a satisfactory simple approach. Periodical BIA determination provides useful informations mainly when the anthropometrical estimation are doubtful and the comparison of data may increase the kinetic reliability.