9 SUMMARY AND DISCUSSION

141Summary and discussion Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by re-current episodes of abdominal pain or discomfort accompanied by disturbed bowel habits. It is among the most frequently occurring functional bowel syndromes, with a prevalence ranging from 5 to approximately 20%. Diagnosis is made according to the Rome criteria. Despite the growing body of literature, the pathophysiology of IBS remains poorly understood. A variety of mechanisms have been proposed in symptom generation, including enhanced visceral sensitivity, disturbed intestinal motility, autonomic dysfunction, mucosal inflammation, altered immune activity, altered processing of afferent sensory information, and psychological disturbances. These alterations probably reflect dysfunction at different levels of the brain-gut axis, a conceptual framework which has recently emerged in an attempt to improve our understanding of the etiology, pathogenesis and clinical expression of IBS. The stud-ies presented in this thesis highlight different aspects of the brain-gut axis in order to gain further insight in the pathophysiological mechanisms underlying IBS