Measurement of the Lymphatic Clearance of the Human Skin Using a Fluorescent Tracer

The lymphatic clearance of the human skin at the instep of the foot was measured in 20 healthy volunteers (mean age ± SD 33.8 ± 10.5 years). Ten microliters of fluorescein isothiocyanate-dextran 150,000 were injected intradermally and the fluorescent light intensity of the deposit was measured 10 min and 24 h after injection by window densitometry. Fluorescent light intensity decreased by 31.2 ± 13.5 arbitrary units (p < 0.0001) or by a factor of 4.1 ± 3.9. Reproducibility was tested 2–6 weeks later in 7 subjects and an intraclass reliability of 0.76 was found. These are the first measurements of the lymphatic clearance of the human skin using a fluorescent tracer. The method is easier and safer than the isotope clearance technique and small areas of the human skin can be investigated. The data found form a basis with which to compare measurements made in patients with different forms of edema.