Assessment of bilateral limb lymphedema by bioelectrical impedance spectroscopy

Objective: The aim of the present study was to determine if the ratio of extracellular fluid (ECF), including the lymph, to that of intracellular fluid (ICF), as measured by bioimpedance spectroscopy (BIS), could be used to assess bilateral lymphedema (LE). Background: The presence of LE is commonly determined as an increase in tissue volume due to the presence of excess lymph relative to the volume of a comparable unaffected body region or to comparative normative data. However, in bilateral LE of the limbs, a comparable body region, the contralateral limb, is also affected, precluding normalization. An alternative is to normalize the increase in lymph volume, as ECF, to that of ICF volume. Methods: Extracellular/intracellular fluid ratios, expressed as the ratio of intracellular impedance (R_i) to extracellular impedance (R ₀), for the limbs of 277 female and 224 male controls were determined from an accumulated database of impedance data. Equivalent data were obtained for an opportunistic cross-sectional sample of 37 female and 5 male participants with bilateral LE of the legs. The ratios of R_i/R₀ in the lymphedematous legs of the affected participants were compared with the equivalent ratios in the unaffected arms of the same participants and with those of the controls using box plots and visualized as bivariate data using tolerance ellipses. Results: Despite R_i/R₀ ratios varying with age, sex, and limb dominance, comparison of the ratio for affected legs (normalized to the ratio in the unaffected arms) with equivalent ratios observed in a control population (as bivariate tolerance plots) was capable of discriminating between 70% and 89% of the participants with LE. Conclusions: Bioelectrical impedance spectroscopy and determination of R_i/R ₀ ratios as indices of ECF/ICF ratios holds promise for the semiquantitative assessment of bilateral LE.