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-III 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.