[Mechanisms of water exchanges: the Starling equation]

This review considers the main mathematical models used in the understanding of transvascular fluid exchanges and oedema formation. Models by Starling, Kedem-Katchalsky and Wiederhielm are briefly described. The main factors which determine the value of the physical parameters involved in these models are the osmotic and interstitial pressures in plasma and tissue. With regard to the regulation of interstitial osmotic pressure, the importance of the presence of mucopolysaccharidic gel in the interstitial compartment creating an exclusion volume for proteins diffusing from plasma is underlined, as well as the importance of lymphatic flow, a parameter neglected in several models of transcapillary exchanges. Consequences of variations in venous hydrostatic pressure, plasma oncotic pressure, endothelial permeability are discussed using the described models. In case of changes combining an increase in venous pressure and permeability and a decrease in plasma oncotic pressure, the importance of correcting venous pressure relatively to protein supply is discussed.