Differentiation of functional venous insufficiency and leg lymphedema complicated by functional venous insufficiency using subcutaneous tissue ultrasonography

Abstract

Objective: To use subcutaneous ultrasonography to differentiate legs with edema because of obesity-related functional venous insufficiency (FVI_ob), immobility-related FVI (FVI_im), secondary lymphedema (LE), LE complicated by obesity (LE_ob), and LE complicated by immobility (LE_im).

Methods: Ninety-nine legs with edema (16 FVI_ob, 32 FVI_im, 22 LE, 9 LE_ob, and 20 LE_im), and 10 normal legs were examined. Subcutaneous tissue ultrasonography was performed at eight points (medial, lateral, upper, lower, thigh, and calf) in each leg. Subcutaneous echogenicity (SEG) and subcutaneous echo-free space (SEFS) were assessed, and each graded as 0, 1, and 2 according to their severity.

Results: In normal legs, SEG and SEFS were graded 0 in almost all parts of the leg. SEG was diffusely increased in FVI_ob, whereas SEG was increased in accordance with gravity in FVI_im (upper medial thigh, 0.6 ± 0.5 vs lower medial calf, 1.2 ± 0.4; P < .001). In LE, SEG was increased in the medial side, particularly evident in upper thigh (upper medial thigh, 1.1 ± 0.4 vs upper lateral thigh, 0.6 ± 0.6; P < .01). SEFS was increased in accordance with gravity in all of these legs (FVI_ob: upper medial thigh, 0.2 ± 0.4 vs lower medial calf, 0.7 ± 0.8; P = .05; FVI_im: upper medial thigh, 0.1 ± 0.2 vs lower medial calf, 1.3 ± 0.7; P < .0001; LE: upper medial thigh, 0.4 ± 0.7 vs lower medial calf, 0.9 ± 0.9; P < .05). The increases of SEG and SEFS in legs with LE_ob or LE_im were diffuse and similar. As determined via stepwise logistic regression analyses, the increases in SEG in the upper medial thigh and SEFS in the lower medial thigh in LE cases, the increases in SEG in the upper lateral thigh and SEFS in the lower lateral thigh in cases with obesity-related leg edema (ie, FVI_ob and LE_ob), and the increase in SEFS in the lower lateral calf in cases with immobility-related leg edema (ie, FVI_im and LE_im) were determined to be significant factors to characterize each leg edema.

Conclusions: Differences in the extent and distribution of SEG and SEFS might help in differentiating LE from FVI_ob and FVI_im, although assessment of LE complicated by obesity vs immobility remains difficult.