Diagnostic evaluation of the irritable bowel syndrome.

New, restrictive criteria discriminate the irritable bowel syndrome (IBS) from normals and other gastrointestinal disorders with a high degree of specificity but lesser sensitivity. The diagnosis is based on positive features that include these criteria. In addition, some structural or biochemical disorders are ruled out by routine tests, whereas others require specialized tests when specific symptoms indicate. Extracolonic and extraintestinal symptoms that often accompany IBS suggest a generalized smooth-muscle or autonomic disorder that may require further investigation as well.