Duodenogastric reflux (DGR) is a poorly defined condition which is difficult to accurately diagnose. There is a definite need for a simple test which can be used to define both the existence and severity of the disease. The long term monitoring of gastric intraluminal pH holds promise in this respect. The first aim is to measure the gastric luminal pH at different levels between the cardia and the pylorus in normal human volunteers and dogs to determine how the pH varies in different parts of the stomach under normal physiological conditions. The pH environment is probably influenced by eating, changes in posture, DGR, gastric emptying and acid secretion, therefore the intraluminal pH environment will be mapped at different sites in the stomach over prolonged periods of different physiologic activity including eating, posture change, induced DGR and altered gastric motility and acid secretion. With this background information, computer assisted analysis of gastric pH data in symptomatic patients will help define whether the disease of pathologic DGR indeed exists and a comparison with existing tests will indicate whether prolonged intragastric pH measurements on their own can be used in diagnosing the condition. Surgical therapy of DGR has included the use of the Roux-en-Y operation which results in profound alterations in gastrointestinal function. We have recently developed an alternative operation (the "duodenal switch") which appears to be more physiologic in that no vagotomy is required and the antro-pyloric mechanism is left intact. These two surgical procedures will be analyzed and compared in both animals and humans. A key feature of the "duodenal switch" involves suppression of acid secretion by a duodenal feedback mechanism. This will be studied using Pavlov pouches in dogs. The results of this project will provide a better understanding of the phenomenon of DGR, more definitive diagnosis of pathologic DGR, and will explore the physiological advantages of a new surgical therapy.