102 - Disorders of Salt and Fluid Balance: Diabetes Insipidus, Cerebral Salt-Wasting Syndrome, and Syndrome of Inappropriate Antidiuresis

Abstract

Maintaining a constant volume and composition of body fluids is crucial for function in all organs and is ultimately essential for the survival of an organism and for cultivating its full spectrum of behavior. Disturbances in water and salt balance at any physiological level can severely impair an individual's life. The brain, as regulative center, as well as the kidney, as the executive organ, can be involved in disorders of salt and water balance. First, this chapter describes the function of the kidney in maintaining water and salt balance at the anatomical, physiological, and molecular level as well as its integration in brain function as the superior regulative center. Second, it describes the pathophysiology of diabetes insipidus, also illuminating the molecular aspects of this condition, and further addresses the issues of diagnostic management and therapeutic strategies. Third, it deals with the different entities of hyponatremia, focusing on cerebral salt wasting and syndrome of inappropriate antidiuresis. After introducing the currently known pathophysiological concepts underlying these disorders, the diagnostic management of hyponatremia is described in detail based on a diagnostic algorithm to overcome the difficulty in the differential diagnosis of the two disorders.