Correlation Between the Severity of Subcutaneous Echo-Free Space and the Amount of Extracellular Fluid Determined by Bioelectrical Impedance Analysis of Leg Edema.

BACKGROUND: Both subcutaneous echo-free space (SEFS) observed by ultrasonography and the ratio of intracellular fluid resistance to extracellular fluid resistance (Ri/Re) calculated from bioelectrical impedance analysis (BIA) represent extracellular edema status in the extremities. We tried to correlate these parameters. METHODS AND
RESULTS: In 70 legs with venous edema (VE) and 68 legs with lymphedema (LE), subcutaneous tissue ultrasonography to determine SEFS severity (range, 0-2) and BIA to calculate Ri/Re were performed. In the calf, SEFS severity showed good linear correlation with Ri/Re, particularly in the lower lateral calf where the mean Ri/Re for LE (SEFS grade 0: 3.2 ± 0.8; SEFS grade 1: 4.0 ± 0.9; SEFS grade 2: 6.3 ± 3.6) and VE (SEFS grade 0: 3.6 ± 0.6; SEFS grade 1: 4.4 ± 1.6; SEFS grade 2: 5.3 ± 2.0) was similar. In the thigh, a mild correlation was confirmed only in LE.
CONCLUSIONS: It may be concluded that SEFS in the lower calf area well represents the local fluid status regardless of the type of edema, but not so in the thigh.