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166 Chapter 7 postprandial propagating events of any kind does not differ between constipated children and adults; and (v) the increase in the postprandial cyclic motor patterns present in healthy adults is absent in these children, as is also seen in constipated adults. High-amplitude propagating sequences Traditionally colonic manometry studies have focused mainly on the presence, amplitude, and frequency of HAPS. These motor patterns are considered the main driving force behind the antegrade mass movement of feces 22 by peristaltic contractions mediated by enteric neural circuits and are associated with spontaneous 23 and chemically induced 24 defecation. The presence of HAPS during colonic manometry, either spontaneous or after bisacodyl provocation, is therefore of importance in determining normal colonic propulsive contractions dependent on enteric neural mechanisms. Indeed, the presence of these motor patterns is used to confirm normal colonic motility and thus to predict success of antegrade enemas through an appendicostomy or cecostomy or to help making decisions in (surgical) management. 14,25 In this study, only two of 18 children showed spontaneous HAPS. While this could be seen as evidence of a potential neuropathy 12 , it is also important to note that HAPS were only observed in half of healthy adults. As we have argued previously 17 , the relative paucity of this motor pattern in many of our healthy controls may result from our current protocol. By recording in an empty colon, we are likely to have removed one of the major stimuli to induce this motor pattern. In animal preparations, distension of the colon initiates propulsive peristaltic contractions mediated by enteric neural circuits 26,27 , with the speed of propulsion dependent on the size of the bolus. 28 Therefore, the absence of HAPS in an empty human colon does not necessarily imply abnormality. For this reason, a more appropriate test of normal propulsive function due to normal enteric neural mechanisms is the challenge with bisacodyl. 29 After administration of bisacodyl, HAPS were identified in 16 of 18 children, indicating that the mechanisms involved in the chemical initiation of these motor patterns are present in most subjects. Thus, although this finding does not mean that these children have normal colonic motility, it suggests that the enteric neural circuits responsible for the chemically triggered peristaltic contractions are functioning normally. One of the advantages of high-resolutionmanometry is that we are now able to characterize many more propagating motor patterns than we could previously identify using the low- resolution recordings. 20 In our high-resolution manometry work in healthy adults, we were able to statistically identify two distinct groups of propagating motor patterns, on the basis of the shape of the component pressure events. The first group included the HAPS, and