Physiopathologie et traitement des troubles fonctionnels intestinaux

Functional bowel disorders (FBD) are chronic digestive symptoms attributable to the lower gastrointestinal tract in the absence of any structural or biochemical explanation. The most common FBD is the irritable bowel syndrome (IBS), in which abdominal discomfort or pain is associated with disordered bowel habits (diarrhoea, constipation or both) or disturbed defecation. IBS pathophysiology is multifactorial and generally related to a “gut-brain axis” dysfunction. Serotonin (5-HT), a neurotransmitter found mainly in the gut, appears to represent a link in IBS pathophysiological processes. Recent studies have also highlighted the potential impact, in the onset of symptoms, of a micro-inflammatory condition and of an immunocompetent cell dysfunction, mainly mast cells, at the enteric nervous system level. In some patients, IBS appears as a post-infectious disorder, following an acute gastroenteritis. Traditional IBS management often relies on a combination of dietary measures, antispasmodic drugs and antidiarrhoeal or laxative drugs. Since it has been demonstrated that it is the main substratum of abdominal pain in a majority of IBS patients, visceral hypersensitivity appears the first therapeutic target. While tricyclic antidepressant agents given at low doses have become an option, the potential role of 5-HT has justified the development of new serotonergic agents, either 5-HT3 antagonists or 5-HT4 agonists, providing global relief of the multiple IBS symptoms. The influence of brain on gut-brain axis dysfunction cannot be omitted and psychotherapy, hypnosis or relaxation are useful, particularly in the most severe patients.