Regulation of salt and water balance

In the period 1945–1965 the key features of the regulation of salt and water balance seemed to have emerged yet the next 20 years revealed an increasing disparity between physiological theory and clinical fact. During the 1980s it was recognised, belatedly, that the physiological defence against excess salt is almost as important as that against depletion and that two main types of hormone were vital in this defence. There was also increasing emphasis on the role of non-renal factors in the regulation of salt and water balance. Despite this rapid progress the paradox remains: all we know about the physiology of sodium balance still does not enable us to explain convincingly its three most obvious disturbances; cardiac, hepatic and nephrotic oedema. In this subject, clinical problems continue to provide the force behind the scientific advances.