Pathogenesis of irritable bowel syndrome.

Irritable bowel syndrome (IBS) is defined as chronic-recurrent abdominal pain in absence of organic lesions. The crucial pathogenetic point is to establish whether pain is related to enhanced sensitivity of the patient or to an abnormal peripheral stimulus originating from the bowel. We can subdivide the patients with abdominal pain into two main groups: the first comprehends those patients with an abnormal response to a normal stimulus (i.e. an enhanced motor response to a meal) (irritable bowel syndrome) and second those patients who have a normal response to an abnormal stimulus (i.e. alimentary factors, laxatives, bile acids) (irritated bowel syndrome). On the basis of our knowledge we can say that the pathogenesis of IBS is complex and not yet completely defined. The crucial point is represented by our capability to discriminate between the "irritable" and "irritated" colon.