Diagnostic approach to suspected irritable bowel syndrome.

Diagnostic activity in patients with suspected irritable bowel syndrome (IBS) should be brief and focussed, limited to investigations that are likely to exclude serious alternative diagnoses and when negative support a positive diagnosis of IBS. The diagnosis of IBS is clinical, and is robust over time, although other symptoms may add to the clinical picture and other symptoms of functional disorders are common. The most important differential diagnoses are celiac disease, colorectal carcinoma and colitis. 'Red Flag' symptoms and signs should be considered indications for full colonoscopy, which should be performed with a low threshold in patients above 50 years of age. Serologic markers are useful to exclude celiac disease, but positive tests must be confirmed with duodenal biopsies.