Vital microscopy and the pathophysiology of deep venous insufficiency.

Insufficiency of the deep venous system of the leg may cause severe disturbances of the skin microcirculation. The pressure in the deep venous system increases markedly during walking when the venous valves are destroyed. This pressure increase is transmitted out through the ankle perforators into the superficial veins of the skin, causing a marked pressure increase in the skin microcirculation, interfering with the normal nutritional circulation. In patients with only superficial venous incompetence, the number of capillaries is unchanged, and the configuration mostly normal. When the capillary pressure is markedly increased, blood components are pressed out through the capillary wall and deposited between the wall and the skin cells. By ordinary capillary microscopy this can be seen as light areas around the capillaries. The capillaries themselves become very enlarged and tortuous, and the number is decreased. One of the most striking findings is the appearance of a <> formation around the nutritional skin capillaries. This halo is caused by a specific microedema which can be demonstrated by microscopic techniques. The edema fluid seems to contain high concentrations of fibrin, other proteins and neutral polysaccharides. The development of the halo formation is most probably due not only to incompetence of the venous but also of the lymphatic system of the affected leg. The normal pathway of nutrients from the capillaries out to the skin cells will be blocked by the oedema, and skin ulcers develop. The good effectiveness of compression bandaging in venous leg ulcers can be explained by a marked reduction of the edema, facilitating the transport of nutrients from the capillaries to the skin cells.