Background: This case-control retrospective study focused on the extracellular water ratio (%ECW) of lymphedemic limbs measured by bioelectrical impedance analysis (BIA) as a possible indicator of the development and severity of unilateral and bilateral leg lymphedema. Methods and Results: BIA was used to evaluate changes in %ECW due to lymphedema in female patients with unilateral secondary leg lymphedema and in healthy controls. Receiver operating characteristic (ROC) analysis was employed to assess the diagnostic ability of %ECW to distinguish leg lymphedema patients from controls. Thirty-eight female patients were eligible for inclusion along with an equal number of healthy control volunteers. The %ECW of the affected leg correlated with leg body water volume (R2 = 0.28) and the water volume difference between affected and unaffected legs (R2 = 0.58). The ROC analysis showed that %ECW had a high diagnostic ability as a screening tool for the development of leg lymphedema (area under the ROC curve = 0.96). A cutoff %ECW value of 40.0% could predict the presence of leg lymphedema with a sensitivity of 81.6% and specificity of 97.4%. Conclusions: %ECW value may be a simple and useful indicator of the development and severity of leg lymphedema. As a screening test, %ECW measurement can predict the presence of unilateral or bilateral leg lymphedema in a single measurement without the need for arm, contralateral leg, or previous measurements as controls.
Keywords: bioelectrical impedance analysis; extracellular water; extracellular water ratio; lymphaticovenular anastomosis; lymphedema.