14781-koppen

204 Chapter 9 compliance have been demonstrated. 22 These high colonic volumes are attributed to a low colonic tone. Similarly, an increased visceral compliance has also been demonstrated in the rectum of children with FC. 23 Although this increased rectal compliance does not seem to be associated with clinical outcome, it does seem common in severe forms of FC. 24,25 Furthermore, colonic dilation has also been suggested to be associated with connective tissue disorders of the intestinal wall. 26 The finding that constipation is common in patients with Ehlers-Danlos syndrome supports this hypothesis. 27 It is likely that connective tissue disorders as underlying causes of constipation are easily missed. Finally, changes in the enteric and extrinsic neuropathic network have been demonstrated in adult patients with intractable constipation. These changes include a reduced number of interstitial cells of Cajal, enteric neurons and enteric glial cells. 28,29 A loss of enteric glial cells has also been described in patients with chagasic and idiopathic megacolon. 29 This suggests that enteric nervous system abnormalities potentially play a role in constipation and findings associated with constipation. To date, it is unclear if colonic dilation is the cause of the dysmotility or if an underlying colonic dysmotility leads to stasis of fecal material which in return results in the development of a distended colon. It is possible that this phenomenon has a multifactorial etiology and that the different clinical features are influenced by each other. This question cannot be completely answered based on the current studies, but it is important to note that dysmotility has been shown to improve after decompression of the colon in previous studies. 30–33 Interestingly, in this sample, a large colonic diameter was associated with prematurely terminating HAPCs, but not with complete absence of HAPCs (colonic inertia). Absence of HAPCs despite administration of bisacodyl is considered to be associated with a severe form of colonic dysmotility. 34 Although prematurely terminating HAPCs are also a sign of dysmotility, at least some degree of coordinated contractile activity can be observed in these patients. This indicates that parts of the neural and muscular networks necessary to coordinate such activity are still functional. Of note, the two patients with the most severe dysmotility did not have the most severe degree of dilation. Hence, the absence of severe dilatation does not exclude severe dysmotility. In addition, the prevalence of megacolon/ megarectum did not differ among children with fully propagating HAPCs, prematurely terminating HAPCs and those without any HAPCs. This demonstrates that, although dilation was associated with dysmotility, dilation was not a prerequisite for dysmotility and not an indicator of dysmotility severity.