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Old 01-07-2012
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GIT Abdominal Distension and Cramps

A 15-year-old otherwise healthy boy presents with a complaint of intermittent abdominal distention, crampy abdominal pain, and excessive flatulence. He first started noticing these symptoms when he moved into his fatherís house, and his stepmother insisted on milk at dinner every night. He has normal growth, has not lost weight, and has no travel history. Which of the following is the most appropriate diagnostic study to diagnose his condition?
a. Barium swallow and upper GI
b. Hydrogen excretion in breath after oral administration of lactose
c. Esophageal manometry
d. Stool pH
e. Serum lactose levels
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Old 01-07-2012
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Hydrogen excretion in breath after oral administration of lactose
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Old 01-07-2012
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b. Hydrogen excretion in breath after oral administration of lactose
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Old 01-08-2012
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Lactase is a disaccharidase localized in the brush border of the intestinal villous cells. It hydrolyzes lactose to its constituent monosaccharides, glucose and galactose. Intestinal lactase levels are usually normal at birth in all populations; however, lactase deficiency is a common, genetically predetermined condition. Lactase activity is not readily increased by the oral administration of substrate or the inclusion of lactose in the diet. The clinical symptoms of lactose malabsorption are due to the presence of osmotically active, undigested lactose, which may act to increase intestinal fluid volume, alter transit time, and produce the symptoms of abdominal cramps, distention, and occasionally, watery diarrhea. Bacterial metabolism of the nonabsorbed carbohydrates in the colon into carbon dioxide and hydrogen may contribute to the clinical symptoms. Acquired lactase deficiency is often associated with conditions of the gastrointestinal tract that cause intestinal mucosal injury (e.g., sprue and regional enteritis). Diagnostic techniques for lactose intolerance include removal of the offending sugar, with a reproduction of symptoms upon reintroduction. Although the ingestion of even small amounts of lactose can be diagnostic if gastrointestinal symptoms occur, the measurement of breath hydrogen is more specific, as it is not affected by glucose metabolism or gastric emptying. Similarly, an acidic stool pH in the presence of reducing substances would be diagnostic. Direct measurement of enzyme levels combined with histologic evaluation helps to differentiate an acquired (secondary versus primary) lactase deficiency in which the intestinal histology is normal.
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