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186 Chapter 8 The identification of long single motor patterns in our current study is of potential interest. They were commonly seen in many children in this study and in our previous study of children with FC in whom we used a water-perfused catheter. 13 Indeed, in our previous study thesemotor patterns were significantly more prevalent in constipated children than in healthy adults 13 . The origin of these motor patterns has not yet been established. However, the characteristics of the pressure waves (duration, amplitude, gradient) that make up the long single motor pattern in health did not differ from those that made up the cyclic motor pattern. 16 As the cyclic motor patterns consisted of pressure waves at 2- 4/min, it is assumed they are generated by interstitial cells of Cajal located in the circular muscle layer and are of myogenic origin. 25–27 Therefore, as the pressure waves in the long single and cyclic motor patterns are similar we have previously speculated that they both share the same underlying myogenic mechanism. 16 Why they are more prevalent in constipated children than healthy adults is not known, but it is possible that in the healthy adult colon the motor pattern is normally supressed. Studies in whole segments of surgically removed human colon show that motor patterns similar to the long single motor patters are prevalent. 18,28 These studies therefore support the hypothesis that the extrinsic neural pathways controlling colonic motor patterns may be impaired in patients with FC. Traditionally, in pediatric studies, the interpretation of a normal colonic manometry recordings is based almost entirely upon the observation of the presence and characteristics of HAPCs. 11 These motor patterns play a key role in defecation and in the mass movements of content around the colon and are therefore of physiological importance. 12,29,30 In our study, HAPCs occurred in the majority of children after administration of bisacodyl and these motor patterns were always accompanied by a sensation of urge to defecate, abdominal cramping and in most cases actual defecation. However, the urge to defecate or defecation itself also occurred after administration of bisacodyl in children in whom no HAPCs were observed, which still led to defecation. Therefore, “normal”motor function should not solely be based on the presence or absence of HAPCs. In the evaluation of colonic manometry, it is important to take the postprandial response into consideration as well. This is currently often done based on visual inspection of the manometry recording. 11 In the future, it would be helpful to apply more standardized methods to evaluate the colonic meal response. It should be noted that when defining HAPCs, the start and end locations of the motor pattern must be taken into account. As seen in this study, motor patterns of sufficient amplitude were not labeled HAPCs because of their length of propagation. However, in nearly every instance these propagating contractions were either observed as starting at the first sensor or ending at the last sensor. In either case the event could have extended beyond the catheter. Therefore technical constraints must be taken into account when defining these motor patterns.