Electric activity of the colon in irritable bowel syndrome: the 'tachyarrhythmic' electric pattern

The etiology of irritable bowel syndrome is unknown. It presents with crampy abdominal pain associated with alternating constipation and diarrhea but with no anatomic abnormality on diagnostic testing. Because the condition is related to motility disturbance, the hypothesis that a disorder of the colonic electromyographic activity is responsible for the colonic motile disorders in irritable bowel syndrome, was investigated.

The electromyographic activity of the sigmoid colon was recorded transcutaneously in 18 patients with irritable bowel syndrome (49.6 +/- 10.2 years, 12 women) and 14 healthy volunteers (47.2 +/- 9.9 years; eight women) by applying three electrodes to the abdominal skin below the umbilicus. The sigmoid colon pressure was measured by means of a saline-perfused tube connected to a pneumohydraulic capillary infusion system.

Slow waves with a regular rhythm were recorded in the healthy volunteers exhibiting the same frequency, amplitude and conduction velocity from all three electrodes. Action potentials (AP) were not registered. The basal sigmoid colon pressure was interrupted by bouts of elevation. In irritable bowel syndrome, the electromyographic rhythm was irregular and the slow wave variables were higher than those of the normal volunteers and were not the same from the three electrodes; occasional AP were also recorded. The sigmoid colon basal pressure was significantly higher, and was interrupted by pressure bouts significantly higher, than those of the volunteers.

Irritable bowel syndrome exhibited a 'tachyarrhythmic' pattern of electromyographic activity with higher slow wave variables than normal and occasional AP. The resulting elevated basal colonic pressure and tone may explain some of the irritable bowel syndrome symptoms. Because diagnostic testing of the irritable bowel syndrome shows no anatomic abnormalities, it is suggested that the cause of irritable bowel syndrome is related to an abnormal focus in one or more of the colonic pacemakers emitting these abnormal waves. However, further studies are required to verify these findings.