Abnormal gallbladder motility in irritable bowel syndrome: evidence for target-organ defect

We have described previously that the gallbladder responds abnormally to infusions of cholecystokinin octapeptide (CCK-8) in patients with irritable bowel syndrome (IBS). To confirm these results and to examine the possible mechanisms, patients with IBS and predominant symptoms of diarrhea or constipation were compared with matched controls. During infusions of CCK-8 at one of three doses, the response of the gallbladder was measured ultrasonographically. The levels of CCK-8 reached in the peripheral circulation and degradation of the peptide in vitro and in vivo were used to evaluate metabolism of cholecystokinin. We confirmed that the gallbladders of patients with IBS responded abnormally to CCK-8; however, the differences were not due to any prereceptor event. Instead, this abnormality in IBS must be explained by an atypical response at the level of the target tissues.