Abstract
Background
Colonic dysmotility is common, yet its nature is not fully understood through low-resolution manometry. High-Resolution Colonic Manometry (HRCM) is capable of revealing detailed motor patterns and their functions can be tested in the clinical setting.
Aims
Our objective was to identify clinically relevant propulsive motor patterns in healthy volunteers and to improve interpretation of motor pattern functions through an in vitro study of equivalent patterns in the proximal rabbit colon.
Methods
Healthy adult volunteers (n=13) received 84-sensor HRCM with different stimuli: balloon distention in proximal and transverse colon, a meal, and bisacodyl in the proximal colon and rectum. In rabbits (n=7) pressure patterns (by HRCM) and motor patterns (by video-recorded diameter changes expressed as spatio-temporal maps) were recorded simultaneously, in vitro, to characterize propulsive pressure patterns.
Results
In adult volunteers, High Amplitude Propagating Pressure Waves (HAPCs) were only observed after stimulation (balloon distention or bisacodyl administration). In contrast, Simultaneous Pressure Waves (SPWs) were observed at baseline. SPWs ranged in amplitude from 5 mmHg to >100 mmHg. SPWs were associated with gas and/or content expulsion and internal sphincter relaxation, consistent with a propulsive and neurogenic nature. Gas expulsion never occurred without SPWs. SPWs spanned between 80% and 100% of the colon. Proximal HAPCs sometimes developed into SPWs. SPWs increased in response to a meal and became prominent in amplitude during balloon distention and after bisacodyl administration. In response to bisacodyl, higher amplitude SPWs were associated with an urge to defecate. SPWs were found to occur in isolation or forming a rhythmic pattern with a dominant frequency of ~ 1 wave/min. When forming a rhythmic pattern, SPWs could inhibit non-propulsive motor patterns suggesting that the absence of a motor pattern can be due to competition from propulsive activity.
Studies in the rabbit model identified SPWs similar to those found in humans, with SPWs caused by fast propagating contractions with velocities greater than 5 cm/s and associated with expulsion of colonic contents.
Conclusions
The literature suggests that SPWs are artifacts or inhibit transit. Here we report that SPWs are the most common propulsive motor activity of the human colon, associated with internal anal sphincter relaxation and gas or content expulsion. SPWs should be considered, together with HAPCs, as an important propulsive motility pattern to characterize when evaluating motor patterns in patients with colonic dysmotility.
Funding Agencies
CIHRHamilton Academic Health Sciences Organization (Ratcliffe)