Studies in human models.

Advances in the development of oral rehydration solutions (ORS) for the treatment of diarrheal disease depend on a knowledge of the disease process itself and of the factors that determine the movement of water and solutes across the gut. The formulation of ORS in current use is based on information derived from a number of different experimental approaches that attempt to take account of these factors. The fate of orally ingested solutions depends first on the processes of gastric emptying that control the rate of entry of fluid to the small intestine and second on the rates of absorption and secretion in the intestine. In the absence of a model that can reliably assess the effects of these two processes together, they are normally investigated separately. The methods of choice for measurement of gastric emptying are gamma scintigraphy and gastric aspiration. Multi-lumen perfusion techniques permit measurement of net flux in short segments of intestine. A promising new technique that takes account of both gastric emptying and intestinal transport involves measurement of accumulation in the circulation of isotopic tracers for water added to ingested solutions. The efficacy of new solutions must, however, ultimately be assessed in clinical trials on patients.