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155 Water-perfused colonic manometry 7 Manometry protocol The manometry protocol in children was similar to the protocol used in adults 13,17,20 , with a few notable exceptions. In adults, because lighter levels of sedation were used, colonic manometry recording commenced within 60 min after catheter placement. In the children, the recording started within 2–4 h after catheter placement, to ensure children were fully awake. In adults, a set meal containing 700 kCal was consumed. In children, the calorie content of the meals differed depending on the age of the child (<12 years: minimum 400 kcal, ≥12 years: minimum 700 kcal). In all subjects colonic manometry was recorded for 2 h in the basal fasting state, followed by a further 2 h after a meal. Then, only in children, after 4 h of recording, bisacodyl (Bisacodyl, Boehringer Ingelheim BV, Alkmaar, The Netherlands) was introduced into the colon via the central lumen of the catheter. The bisacodyl dose varied depending on body weight (<50 kg: 5 mg, ≥50 kg: 10 mg bisacodyl). Afterwards, the recording continued for another hour. If the first dose did not induce HAPS within 30 min, a second dose of bisacodyl (twice the initial dose; 10 or 20 mg) was administered and the recording continued for an additional 30–60 min (until HAPS were observed). Analysis of manometric data Manual analysis All analyses of manometric data were performed using software (PlotHRM) developed by one of the authors (LW). PlotHRMwas written in Matlab© (The MathWorks, Natick, MA, USA) and JavaTM (Sun Microsystems, Santa Clara, CA, USA). In each manometry tracing, artifacts and simultaneous pressure events that spanned all recording channels were digitally removed as described previously. 13,17 Each of the pressure traces was then visually inspected by one of the authors (PD) for propagating activity, defined as pressure events that occurred in ≥4 adjacent channels in the fiber-optic data and ≥3 in the water-perfused data (i.e. ≥3 cm in both data sets). If a pressure event returned to baseline before the pressure event in the adjacent channels started, then the two events were not considered part of the same propagating motor pattern. Propagating motor patterns were classified on the basis of whether they occurred cyclically or as single events, whether their propagation was anterograde (anally propagating) or retrograde (orally propagating), by their propagation velocity and by the distance over which they traveled. In the previously published data of colonic motor patterns recorded in healthy adults, four commonly seen and distinct propagating motor patterns were defined: