Characterization of a hyperactive segment at the rectosigmoid junction.

During a study of intraluminal motor patterns of the colon and rectum, spontaneous wave activity of a continuous complex type was observed at the rectosigmoid junction in constipated subjects. To assess the frequency and characteristics of this hyperactive segment, 36 subjects with colonic motor disorders and 12 healthy controls were studied. Eighteen of 24 patients with constipation (75%) and 1 of 7 subjects with asymptomatic diverticulosis exhibited a persistent hyperactive segment at the rectosigmoid junction. Neither secretin nor cholecystokinin influenced the wave activity of the hyperactive segment. In contrast, atropine and glucagon inhibited markedly all wave activity and decreased the motility index of this segment significantly, suggesting overactivity of the muscarinic effector cells. It is concluded that a segmental area of overactivity exists at the rectosigmoid junction in most constipated subjects regardless of their underlying disorders.