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Negative hydrogen breath test
11%
3/28
Abnormal small bowel biopsy
7%
2/28
Positive hydrogen breath test
71%
20/28
Positive technetium 99 scan
Abnormal abdominal ultrasound
0%
0/28
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This patient presents with lactose intolerance. On testing, she would have a positive hydrogen breath test. Lactose intolerance is the inability to digest lactose, a common disaccharide, due to a deficiency of the digestive enzyme lactase. It causes osmotic diarrhea whenever lactose is ingested and produces abdominal pain, flatulence, and diarrhea. It is commonly diagnosed by a positive hydrogen breath test. The hydrogen breath test is performed by administering a small amount of lactose and measuring hydrogen breath levels every 15, 30 or 60 minutes for three hours. If the level of hydrogen rises above 20 ppm, the patient is diagnosed with lactose intolerance. Treatment is avoidance of dairy products or lactase replacement prior to meals containing lactose. Swagerty et al. review the pathophysiology, diagnosis, and management of lactose intolerance. They state that the diagnosis can usually be made with a careful history supported by dietary manipulation with subsequent resolution of symptoms. If necessary, the diagnosis can be confirmed by using a breath hydrogen or lactose tolerance test. Treatment consists primarily of avoiding lactose-containing foods. Lactase enzyme supplements may be helpful. Ji et al. performed a population based study to examine the association between lactose intolerance and the risk of lung, breast, and ovarian cancers. Of the 22,788 individuals with lactose intolerance, the risks of lung (SIR=0.55), breast (SIR=0.79), and ovarian (SIR=0.61) cancers were significantly decreased. They hypothesize that the protective effects against these cancers may be related to lactose avoidance. Illustration A demonstrates the geographical distribution of lactose intolerance. Note that many Asian countries such as China have a very high percentage. Illustration B is a graphical representation of the hydrogen breath test. Illustration C demonstrates the results of the hydrogen breath test in a lactose intolerant patient. Incorrect answers: Answer 1: Patients with lactose intolerance will have a positive hydrogen breath test. Answer 2: Patients with lactose intolerance have normal histology seen on small bowel biopsy. Answer 4: A positive technetium-99 scan is seen in patients with Meckel's diverticulum. Answer 5: An abnormal abdominal ultrasounds would be seen in patients with intussusception but not in lactose intolerance.
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