Colonic electromyography in chronic constipation

Myoelectric activity of the sigmoid has been studied in 12 patients with chronic nonorganic constipation and 10 control subjects. All patients showed total gastrointestinal transit time longer than 96 h, with left-colonic or rectocolonic slowed transit. Electrical and mechanical activity was recorded by means of an intraluminal probe with bipolar suction electrodes and open-ended tips. Two groups of frequencies of slow waves, a slower rhythm at ~3 cycles/ min and a faster rhythm at ~6 cycles/min were recorded in patients and control subjects. The mean frequency of the slower rhythm was significantly (p < 0.005) higher in patients with constipation than in control subjects, whereas the frequency of the faster rhythm and the incidence of both rhythms were similar in the two groups. Mechanical activity showed no difference in terms of motility index and percentage of activity between patients and control subjects. Results of the study indicate that patients with left colonic constipation show an increase in frequency of the slower colonic rhythm in the very segment in which slowing down of transit occurs. It is suggested that the higher slow-wave activity in the sigmoid induces an increase in segmenting contractions and therefore may be responsible for the slowing down of intestinal transit.