Etiology and pathophysiology of irritable bowel syndrome and chronic constipation

Functional gastrointestinal (GI) disorders are collections of symptoms attributable to the GI tract in the absence of mucosal, structural, or biochemical disease. Two of the most common disorders, chronic constipation and irritable bowel syndrome (IBS), have common etiopathogenetic features-notably psychosocial disturbances, dysmotility, and heightened sensitivity. In some patients with IBS, there is an association with a postinfective state. In constipation, transit disorders and abnormal evacuation represent disturbances of function that are amenable to therapy. This review is an update of the mechanisms and pathophysiology of these disorders. IBS and constipation are defined, and control of gut motility and sensation and their disturbances in these disorders are reviewed along with the mechanisms and pathophysiology of IBS and constipation.