Age-related diurnal changes of dermal oedema: evaluation by high-frequency ultrasound.

Using high-frequency ultrasound, we measured the influence of gravitational stress on skin echogenicity in 22 young (age range 17-27; median 19) and 22 elderly (age range 75-100; median 87) healthy adults. B-mode ultrasound images were obtained from the medial malleolus, lateral calf, anterior thigh, volar forearm and the medial aspect of the arm three times daily: in the morning, immediately before rising, and 2 and 12 h later. The echogenicity was measured by counting the number of low echogenic pixels in the image. Pronounced changes of low echogenic pixel numbers were seen in the areas exposed to high gravitational stress, i.e. the ankle and calf. In the young age-group echogenicity of the skin increased steadily during the day, whereas in the elderly population echogenicity decreased 2 h after getting up in the morning, and subsequently returned to the baseline level. In a control group of 10 people (aged 17-83; median 18), who remained in the supine position throughout the day, the echogenicity of the skin remained unchanged. As the echogenicity of the dermis is inversely related to the amount of fluid it contains, our results indicate that young skin responds to gravitational stress by fluid depletion. In the skin of the elderly, the mechanism of fluid removal appears to be defective. The impaired protection against the development of intradermal oedema in the elderly may predispose to the development of lipodermatosclerosis and leg ulceration.