SIGMOID AFFERENT MECHANISMS IN PATIENTS WITH IRRITABLE-BOWEL-SYNDROME

Up to 60% of patients with IBS have lowered perception thresholds in t he rectum to balloon distension. The current study sought to test the hypothesis that IBS patients with normal perception thresholds in the rectum show hypersensitivity of afferent pathways in the sigmoid colon . Eleven healthy normal subjects and eight IBS patients with normal re ctal perception thresholds underwent a balloon distension protocol in the sigmoid and rectum. Discomfort thresholds, receptive relaxation, c ompliance, and referral patterns were measured. Although IBS patients had significantly lower discomfort thresholds in the sigmoid when meas ured as volume, pressure, and wall tension, thresholds were similar to normals. Receptive relaxation and dynamic compliance were significant ly decreased in IBS patients in the sigmoid. Referral patterns were si milar during sigmoid distention in IBS patients in comparison to norma ls. Despite normal perception thresholds in rectum and sigmoid, IBS pa tients show evidence for alterations in rectosigmoid afferent mechanis ms. In the sigmoid, this is seen in the form of reduced reflex relaxat ion and compliance and in the rectum in the form of altered viscerosom atic referral.