Evolving concepts on inflammatory bowel disease. Are we happy with the present nosology?

The term inflammatory bowel disease traditionally comprises ulcerative colitis, Crohn's disease and indeterminate colitis, an intermediate variant of the two major forms. The term is commonly used in the literature and in clinical practice even though it has never been revised in a Consensus Conference. The present nosology of inflammatory bowel disease seems not to be entirely satisfactory as it is limited to chronic diseases only and does not include several recently described idiopathic inflammatory bowel disorders. Although the aetiology of inflammatory bowel disease remains unknown, both ulcerative colitis and Crohn's disease are characterized by a similar pathogenesis which consists in a persistent intestinal inflammation resulting from disregulation of the gut mucosal immune system. The pathogenetic mechanisms could, therefore, provide a suitable criterion for the classification of idiopathic inflammatory bowel disease. A revised classification of inflammatory bowel disease is thus proposed. It seems reasonable to subclassify inflammatory bowel disease into acute and chronic forms. Acute forms should include the sudden attacks of ulcerative colitis and Crohn's disease with rapid and complete resolution and the so-called "acute self-limited colitis". The chronic forms should comprise, besides the classical forms of ulcerative colitis, Crohn's disease and indeterminate colitis, also other idiopathic inflammatory bowel conditions such as collagenous colitis, lymphocytic colitis and eosinophilic gastroenteritis.