Clinical Reviews: The Small Intestine, Nutrition, And MalabsorptionLactose Intolerance Problems in Diagnosis and TreatmentShaw, A. D. B.Sc.(Hons), F.R.S.H.; Davies, G. J. B.Ed., M.Sc., Ph.D., F.R.S.H.Author Information From the Nutrition Research Centre, School of Applied Science, South Bank University, London, United Kingdom. Address correspondence and reprint requests to A. D. Shaw, Nutrition Research Centre, School of Applied Science, South Bank University, 103 Borough Road, London Southern 0AA, UK. Journal of Clinical Gastroenterology: April 1999 - Volume 28 - Issue 3 - p 208-216 Buy Abstract Lactose malabsorption and lactase deficiency are chronic organic pathologic conditions characterized by abdominal pain and distention, flatulence, and the passage of loose, watery stools. Though malabsorption of the sugar lactose is determinable by breath hydrogen test or jejunal biopsy, intolerance can only be confirmed by challenge with lactose-containing food, the response to which may not be immediate. The difficulty of making a positive diagnosis of these conditions has led to a proportion of lactose-intolerant patients being misdiagnosed with irritable bowel syndrome (IBS), which has a remarkably similar symptom complex and for which there is no current pathophysiologic marker. The incidence of the two disorders is approximately equal, but the actual proportion of patients with IBS incorrectly diagnosed in this way varies as a function of the methodology used. Once correct diagnosis is established, introduction of a lactose-free dietary regime relieves symptoms in most patients. Symptom similarity and the resultant incorrect diagnosis of IBS may explain the refractory nature of some patients labeled as IBS who remain largely unaware of the relationship between food intake and symptoms. © 1999 Lippincott Williams & Wilkins, Inc.