Indirect prediction of total body water content in healthy adult Beagles by single-frequency bioelectrical impedance analysis

OBJECTIVE To develop equations for prediction of total body water (TBW) content in unsedated dogs by combining impedance (resistance and reactance) and morphological variables and to compare the results of those equations with TBW content determined by deuterium dilution (TBWd). ANIMALS 26 healthy adult Beagles. PROCEDURES TBW content was determined directly by deuterium dilution and indirectly with equations developed from measurements obtained by use of a portable bioelectric impedance device and morphological variables including body length, height, weight, and thoracic and abdominal circumferences. RESULTS Impedance and morphological data from 16 of the 26 dogs were used to determine coefficients for the following 2 equations: TBW1 = -0.019 (BL2/R) + -0.199 (RC + AC) + 0.996W + 0.081H + 12.31; and TBW2 = 0.048 (BL2/R) + -0.144 (RC + AC) + 0.777W + 0.066H + 0.031X + 7.47, where AC is abdominal circumference, H is height, BL is body length, R is resistance, RC is rib cage circumference, W is body weight, and X is reactance. Results for TBW1 (R-1(2) = 0.843) and TBW2 (R-2(2) = 0.816) were highly correlated with the TBWd. When the equations were validated with data from the remaining 10 dogs, the respective mean differences between TBWd and TBW1 and TBW2 were 0.17 and 0.11 L, which equated to a nonsignificant underestimation of TBW content by 2.4% and 1.6%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that impedance and morphological data can be used to accurately estimate TBW content in adult Beagles. This method of estimating TBW content is less expensive and easier to perform than is measurement of TBWd, making it appealing for daily use in veterinary practice.