Evidence that abnormal myoelectrical activity produces colonic motor dysfunction in the irritable bowel syndrome.

Although the irritable bowel syndrome is characterized as an abnormality in colonic motor activity occurring in response to certain stimuli, the etiology of this disorder is unclear. The purpose of this study is to determine the relationship of altered slow wave activity and the abnormal motility of the distal colon seen in patients with the irritable bowel syndrome. Myoelectrical activity was recorded using a bipolar electrode clipped to the distal colonic mucosa and motor activity was measured by perfused catheters. Colonic slow waves and contractions were present at two frequencies, 6 and 3 cycles per min. The slow wave frequency seemed to determine the frequency of colonic motor activity. Patients with the irritable bowel syndrome had increased 3-cycle per min slow wave activity in the basal state (P less than 0.001). However, no difference in basal 3-cycle per min motor activity was present between the two groups (P greater than 0.05). When colonic motor activity was increased with cholecystokinin or pentagastrin, patients with irritable bowel syndrome showed a marked increase in 3-cycle per min contractile activity, occurring simultaneously with 3-cycle per min slow wave activity. These studies suggest that increased colonic 3-cycle per min slow wave activity in patients with the irritable bowel syndrome may be the basic abnormality that leads to colonic motor dysfunction in response to various physiological stimuli.