Pathophysiology of chronic constipation and IBS

The pathophysiology of chronic constipation and irritable bowel syndrome (IBS) involves consideration of disturbances in colonic sensorimotor activity, often resulting from disordered extrinsic and/or intrinsic innervations. The mechanisms by which normal colonic activity is altered to cause constipation or IBS are complex, as are the enteric neuropathologic changes that are present in some patients with slow-transit constipation and the serotoninergic disturbances in patients with IBS. Using normal colonic motor patterns and functions as a starting point, this article explores these processes in some detail. It also addresses the assessment of colonic sensorimotor function, the causes of slow-transit constipation, the role of high-amplitude propagated contractions and loss of interstitial cells of Cajal in constipation, the role of serotonin in the gut, and the serotoninergic disturbances in IBS.