14781-koppen

169 Water-perfused colonic manometry 7 explain their increased presence in a proportion of these children. Specific experiments need to be planned to test this hypothesis, which may have important consequences for clinical diagnosis, treatment, and management. Potential limitations and criticism of the study design and interpretation of data There are some obvious limitations that need to be taken into account when interpreting these data. First, we have compared the motor patterns in constipated children to those recorded in healthy adults. In an ideal world, our comparative data would come from healthy children. However, currently that is not ethically possible and it is unlikely to ever be so with this technique. Therefore, as we have done before 42 , we have to use the next best option, healthy adults. While it could be argued that the numbers of the identified motor patterns may differ between healthy adults and healthy children, it is unlikely to explain the differences observed in this study. We have chosen to compare our pediatric data with the only available adult studies utilizing high-resolution colonic manometry while defining the four main motor patterns (HAPS, cyclic, short single and long single) that were previously defined. 17 Another limitation of our study is that in the pediatric patients, different protocols were used to determine colonic transit time. In addition, in some of these severely constipated children, parents did not permit the measurement of colonic transit if the procedure required their child to stop their constipationmedication, suchwas their fear of deterioration of symptoms. Indeed laxatives were taken by some of those children who underwent the transit study. Consequently, we were not able to categorize all patients as either slow-transit constipation or outlet obstruction. The results, however, have shown that the observed colonic motor abnormalities were similar between the studied children, indicating that while there are differences in colonic transit time, the colonic anomalies were consistent. In addition, the impaired postprandial response found in adult slow-transit constipation patients was also observed in the studied pediatric patients, suggesting that these children show similarities with the adult patients. Another potential criticism is the fact that the data in children were recorded with a water- perfused catheter, while in adults a fiber-optic manometry catheter was used. The recording fidelity of both systems is likely to differ, and there may well be differences in the amplitude of the pressure events recorded. However, water-perfused catheters detected the long- single motor patterns in children. Since the characteristics of the pressure events that make up these motor patterns do not differ from those that make up the cyclic motor pattern, it is unlikely the catheter could record one without the other. In addition, non-propagating pressure events were recorded in every child. The failed meal response in children was