Microvascular changes in venous disease: an update.

In an overview the microvascular involvement in chronic venous insufficiency (CVI) is described. Microangiopathy in the lower leg areas is characterized by the presence of typical enlarged and ramified blood capillaries, reduced capillary number, microvascular thrombosis and obliterations, and/or increased permeability of microlymphatics. Transcutaneous oxygen tension (tcPO2) is decreased and directly correlated to the number of perfused capillaries, whereas laser Doppler flux is enhanced. This apparent paradox may be explained by hyperperfusion in the deeper skin layers (mainly shunt vessels) and hypoperfusion in the superficial nutritive vessels. Microvascular changes are of patchy distribution. Trophic changes up to overt venous ulceration are mainly caused by microvascular ischemia and edema formation due to increased capillary permeability and deficient lymphatic drainage.