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Gastric emptying of nondigestible solids in the fasted dog

Gastric emptying of nondigestible solid particles was studied in the fasted dog. Particles of varying sizes (0.5-6.4 mm), density (0.5-2.9 gm/cm3), and surface characteristics were coadministered orally with 50 mL of saline and collected from a permanent duodenal cannula implanted approximately 15 cm from the gastroduodenal junction. The phase of the motility pattern was ascertained by the appearance of bile, which occurs during phase II, as well as by mucus discharge, which stops at the onset of phase I. A lag phase, due to the 'quiet' phase I, was observed in the gastric emptying of coadministered saline. This is in contrast with gastric processing of large volumes (i.e., greater than 200 mL) which can usually be approximated by first-order discharge. Most coadministered saline was discharged before the solid particles. The pH of the duodenal effluent was elevated approximately 1 pH unit during mucus discharge and its pH can be as high as 8.3. In the fasted dog, gastric emptying of nondigestible particles closely followed the gastric motility patterns. The onset of discharge of the particles correlated with the late phase II and the phase III activity. Except for a few cases, which took two migrating motor complexes (MMC), greater than 90% of administered particles was discharged from the stomach after one MMC. The discharged particles were entrapped within mucous plugs. In the fasted state, gastric emptying of nondigestible particles appeared to be independent of size, density, and surface characteristics. Mucus seems to play a significant role in the distribution and discharge of the administered particles.