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Abstract
Background: The last part of phase III of the migrating motor complex (MMC) is characterized by retroperistalsis in the descending duodenum. This study focused on MMC-related juxtapyloric peristalsis. Methods: Antroduodenal manometry was performed in 10 healthy subjects. Pressure was recorded in the distal antrum and in four consecutive subsegments (DS1-DS4), 15 mm each, in the juxtapyloric duodenum. Results: In the period with ongoing antral phase-Ill activity (early duodenal phase III) the antral pressure waves were antegrade, but in the juxtapyloric duodenum (DS1) retrograde waves predominated (median, 66%; interquartile range (IQR), 33–83%); that is, most duodenal pressure waves were directed against the antral ones. More distally, in DS3 and DS4, only 17% and 25% (IQR, 0–17, 0–33%, respectively) of the pressure waves were retrograde in this period. After the end of antral phase III– that is, in late duodenal phase III–the proportion of retrograde pressure waves increased successively to 91.5% (IQR, 66–100%) in DS2, 74.5% (IQR, 50–100%) in DS3, and 66% (IQR, 8.2–95.8%) in DS4, respectively, before the onset of duodenal motor quiescence. In phase II antegrade pressure waves predominated (63–76%, medians) in all four duodenal subsegments examined. Conclusions: During the interdigestive phase III the antral perstalsis is antegrade, but most juxtapyloric duodenal pressure waves are retrograde; that is, antral and duodenal contractions are on a collision course. In the proximal part of the descending duodenum the end of duodenal phase III shows retroperistalsis after the onset of phase I in the gastric antrum. These motor patterns may be important for regulation of the chemical milieu in the juxtapyloric area.