Revisiting concepts of visceral nociception in irritable bowel syndrome.

BACKGROUND AND OBJECTIVE: Irritable bowel syndrome (IBS) is a common disorder characterized by abdominal pain related to defecation with a change in bowel habit. Patients with IBS often exhibit increased visceral sensitivity, which can be tested clinically by rectal balloon distension procedures. This paper aims to give an overview of mechanisms involved in visceral hypersensitivity in IBS by reviewing recent literature. DATABASES AND DATA TREATMENT: A literature search in the electronic databases Pubmed and MEDLINE was executed using the search terms 'visceral pain' or 'visceral nociception' or 'visceral hypersensitivity' and 'irritable bowel syndrome.' Both original articles and review articles were considered for data extraction. RESULTS: Recent advances in molecular neurophysiology provide knowledge to better understand the underlying mechanism in pain generation in the human gut, in particular, in IBS patients. Sensitization of peripheral nociceptive afferents, more specifically high-threshold afferents, has been proposed as one of the principle mechanism in the development of visceral hypersensitivity. On the other hand, central mechanisms also play an important role. In terms of clinical testing of visceral perception, considerable discrepancies remain, however, across different centres. CONCLUSION: Alterations in the modulatory balance of pro- and antinociceptive central processing of noxious peripheral input may serve as in integrative hypothesis for explaining visceral hypersensitivity in IBS. Nevertheless, it remains troublesome to estimate the contribution of central and peripheral factors in visceral hypersensitivity, posing a challenge in determining effective therapeutic entities