Spatial and temporal organization of pressure patterns throughout the unprepared colon during spontaneous defecation.

Abstract

The aim of this study was to examine colonic motor events associated with spontaneous defecation in the entire unprepared human colon under physiological conditions. In 13 healthy volunteers a perfused, balloon-tipped, 17-lumen catheter (outer diameter, 3.5 mm; intersidehole spacing, 7.5 cm) was passed pernasally and positioned in the distal unprepared colon. In the hour before spontaneous defecation, there was an increase in propagating sequence frequency (p = 0.04) and nonpropagating activity when compared to basal conditions (p < 0.0001). During this hour the spatial and temporal relationships among propagating sequences demonstrated a biphasic pattern. Both the early (proximal) and late (distal) colonic phases involved the whole colon and were characterized by respective antegrade and retrograde migration of site-of-origin of arrays of propagating sequences. There was a negative correlation between propagating sequence amplitude and the time interval from propagating sequence to stool expulsion (p = 0.008). The colonic motor correlate of defecation is the colonic propagating sequence, the frequency and amplitude of which begin to increase as early as 1 h before stool expulsion. During the preexpulsive phase, the spatial and temporal relationship among the sites of origin of individual propagating sequences demonstrate a stereotypic anal followed by orad migration, which raises the possibility of control by long colocolonic pathways.