Diameter of inferior caval vein and impedance analysis for assessment of hydration status in peritoneal dialysis

In 19 stable peritoneal dialysis (PD) patients, hydration status was evalua ted by measurement of vena cava diameter (VCD) and bioelectrical impedance analysis (BIA) variables: intracellular water (ICW), extracellular water (E CW), and total body water (TBW). We investigated whether BIA can replace VC D. VCD did not correlate with TBW but correlated moderately with ECW/TBW (r = 0.42; 0.025 < p < 0.05) and ICW/ECW (r = -0.47; p < 0.025). Patients wit h underhydration (n = 4; VCD < 8 mm/m(2)) revealed limits for BIA variables as ICW/ECW (> 1.50) and ECW/TBW (< 0.40). The same held true for overhydra tion (n = 5; VCD > 11.5 mm/m(2)): ICW/ECW (< 1.50) and ECW/TBW (> 0.40). Al though the positive predictive value of ICW/ECW and ECW/TBW for both under- and overhydration was only 50% and 54%, respectively, there were no false negative values. Although BIA cannot replace VCD in PD patients, the revers e holds true as well. Combining BIA and VCD may lead to a better estimation of hydration status because both techniques provide complementary informat ion.