Human duodenal phase III MMC activity is not predominantly retroperistaltic

Abstract

Background: Phase Ill MMC (P-Ill) activity has been said to be primarily retropedstaitic in the proximal duodenum, whilst the distal duodenum has not been studied. Manometrywith high temporal and spatial resolution gives more detailed insights into luminal mechanics than standard techniques, and expressing the pressures as colour contour plots in three dimensions (pressure/time/distance) allows better visual appreciation of pressure patterns. Methods: Human duodenal P-Ill activity was examined in 9 healthy young volunteers (7M, 2F) with these two techniques. During fasting a multilumen assembly was positioned so that the most proximal manometric sidehole was in the distal antrum. After a 4.5 cm interval, a chain of 18 sideholes at 1.5 cm intervals and a 20th sidehole3 cm beyond this spanned the duodenum. Pressures were recorded until the occurrence of a duodenal P-III. For analysis the duodenum was divided by length into proximal (P) and distal (D) halves; and P-Ill was divided into early (E) (first 0.5-1 min) and late (L) (last 0.5-1 min) components. Duration, frequency, direction end velocity of propagation of pressure waves were assessed. Results: Contour plot analysis of 180 pressure wave sequences(PWS)revealed that the majority (121) were purely antegrade. Only 2 PWS were completely retrograde, whilst 57 had bidirectional components. Ten of these 57 PWS were complex in pattern, apparently branching to become2 separate PWS. As in previous studies, fewer bidirectional PWS occurred in early compared to late P-Ill (E 14 vs L 43 of 57), but they did not differ in occurrence between proximal and distal duodenum (P 31 vs D 24 of 57). Propagation velocity was faster in late compared with early P-Ill (E 17,05vs L 28.50 mm.s1, P= 0.006), but did not differ between proximal and distal duodenum. Contour plot analysis also indicated that PWS had a spatially consistent segmental pattern within the duodenum. P-Ill duration was longer in the distal than the proximal duodenum (P 5.21 -+ 1.02 vs D 6.44 _+ 1.02 mins, P=0.046); whereas the frequency of pressure waves did not differ along the duodenum (P 11.3 vs D 11.85 waves.rain1).Conclusion:Duodenal P-Ill is not a homogenous phenomenon, and in contrast to previous studies, does not appear to primarily constitute a retroperistaltic pump. Contour plot analysis is a useful tool for interpreting intraluminal pressures along the gut, and may have the potential to improve the sensitivity and specificity of clinical motility studies.