ABSTRACT
Irritable bowel syndrome is a highly prevalent condition responsible for almost one third of visits to the gastroenterologist and huge expenses for diagnosis, treatment and loss of working days. A unique pathophysiologic mechanism has not been elucidated yet and several possibilities have been proposed such as senso-perception and motor disturbances, the effect of stress and anxiety, serotonin receptor failures, activation of abnormal brain areas and pain modulation differences, among others. The absence of a biological marker has led the investigators to consider this syndrome as an exclusion diagnostic condition, once the organic diseases have been discarded The changes in gut microbiota have recently raised great interest among gastroenterologists. The study of the small intestinal bowel overgrowth syndrome, the effect of antibiotics upon the flora, the recognition of post-infectious irritable bowel syndrome and the action of probiotics, together with the effect of malabsortion of diet carbohydrates have brought some new light in our knowledge. The present update will focus on the published evidence about the subject, bearing in mind that the mechanisms elicited here are only suitable for a subgroup of patients.