Metabolic problems associated with gastrointestinal and pancreatic disease.

With the skin and special senses, the gastrointestinal tract is unique in its exposure to the changes and vicissitudes of the external environment. However, fine control of all aspects of gut function via neuronal and endocrine mechanisms is essential for adequate nutrition through digestive and absorptive processes. Recent chemical studies have resulted in the isolation and elucidation of a wide range of biologically active gut peptides. The gastrointestinal tract is the largest endocrine organ of the body and regulates carbohydrate metabolism (the entero-insular axis) in addition to protein and fat metabolism. Disturbance of gut function by any disease process is therefore likely to have profound consequences on metabolic and nutritional processes, in addition to acid-base and fluid balance. Clearly, it is beyond the scope of a single chapter to present a comprehensive clinical review of this subject. Emphasis will be placed only on malnutrition, maldigestion and malabsorption, whilst obesity—a heterogenous process in which the gut undoubtedly plays a role—will not be discussed. Consideration of treatment may appear to be brief, but the vast subjects of enteral and parenteral nutrition are outside the present remit.