We describe the anatomy and function of the gastroesophageal barrier in the piglet. Male piglets underwent dissection (N = 6) and gastroesophageal muscle layer histometry (N = 6). Sedated, nonintubated animals (N = 13) underwent four-probe perfusion esophageal manometry and the pressure profiles were related to the muscular thickness in the four quadrants. Hiatal and gastroesophageal anatomy are similar to our own. The muscle is thicker at the point where the clasp (on the right side) and sling fibers (on the left) concentrate. The pressure profiles were axially and radially asymmetric in coincidence with the thickness variations of the corresponding muscle layers. Sphincteric pressure was recorded as a plateau, whereas diaphragmatic crural pressure appeared as phasic oscillations in synchrony with respiration. The sphincter relaxed upon deglutition. In conclusion, the gastroesophageal structure and physiology are so similar in men and piglets that piglets are excellent models for research in this area.

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Up to a certain volume, the motor responses of the healthy esophagus to distension with neutral or acid fluids were similar. Acid clearance was more a function of the amount of acid present than of the motor response elicited by its presence. Only when the amount of acid was large, esophageal motor response was worse than that elicited after equivalent volumes of neutral fluid. The present evidence suggests that long episodes of reflux in pH tracings might reflect large volumes of refluxate as well as disturbed motor function.

The esophagus affected by acid reflux, with or without esophagitis, was capable of near-normal motor responses after boluses of saline. Reflux impaired the peristaltic response to acid, and the effect was more pronounced when reflux and esophagitis were both present. The acid clearance time was also strikingly prolonged in the presence of reflux and esophagitis. The results suggest that long episodes of reflux seen on pH tracings from individuals with esophagitis might be secondary both to acid-related motor dysfunction and large volumes of refluxate.