A 60-year-old woman comes to the office with intermittent flatulence, crampy abdominal pain, and watery diarrhea. Her symptoms started 2 months ago after she recovered from an episode of acute gastroenteritis associated with nausea, vomiting, and diarrhea. The patient's symptoms are worse after drinking "too much milk." She usually has 1 or 2 glasses of wine every evening with dinner. Physical examination is unremarkable. Initial laboratory evaluation, including serum chemistries, blood counts, stool cultures, and studies for ova and parasites, is negative. Which of the following is most likely decreased in this patient?

Question

A 60-year-old woman comes to the office with intermittent flatulence, crampy abdominal pain, and watery diarrhea.  Her symptoms started 2 months ago after she recovered from an episode of acute gastroenteritis associated with nausea, vomiting, and diarrhea.  The patient's symptoms are worse after drinking "too much milk."  She usually has 1 or 2 glasses of wine every evening with dinner.  Physical examination is unremarkable.  Initial laboratory evaluation, including serum chemistries, blood counts, stool cultures, and studies for ova and parasites, is negative.  Which of the following is most likely decreased in this patient?

Quizplus · Accepted Answer

This patient's presentation with flatulence, crampy abdominal pain, and watery diarrhea after consuming dairy products (eg, milk) is consistent with lactose intolerance. The most common cause of lactose intolerance is lactase nonpersistence, which is especially prevalent in Asian and African populations and is characterized by declining lactase expression in adulthood. This patient's lactose intolerance is most likely due to secondary lactase deficiency, an acquired condition resulting from inflammation/infection (eg, bacterial overgrowth, infectious enteritis, Crohn disease) that causes injury to the mucosal brush border of the small bowel where lactase is expressed. Lactase deficiency results in incomplete hydrolysis of lactose into the monosaccharides glucose and galactose. The fermentation of undigested lactose by gut bacteria leads to increased production of short-chain fatty acids (eg, acetate, butyrate, propionate) that acidify the stool (decreased stool pH). During this process, hydrogen gas is also produced, leading to increased breath hydrogen content (Choice A). In addition, the high amounts of undigested lactose in the bowel lead to elevated stool osmolality, which attracts excess water in the bowel lumen, causing osmotic diarrhea (Choice D). (Choice B) Inflammation/infection of the small intestine may lead to fat malabsorption, resulting in steatorrhea (eg, greasy, malodorous stool that is difficult to flush), weight loss, and increased fecal fat content. Fat malabsorption does not typically occur in patients with lactase deficiency. (Choice C) Reduced pancreatic enzyme production (exocrine insufficiency) can occur with chronic pancreatitis, which is seen frequently in individuals with chronic alcoholism. Pancreatic enzyme levels are not affected by secondary lactase deficiency. Educational objective: Lactose intolerance presents with flatulence, crampy abdominal pain, and watery diarrhea after dairy product consumption. It can be acquired by inflammatory/infectious conditions that injure the mucosal brush border of the small intestine where lactase is expressed. Studies can show increased breath hydrogen content, reduced stool pH, and elevated stool osmolality. __________ References: Lactose intolerance in adults: biological mechanism and dietary management. (http://www.ncbi.nlm.nih.gov/pubmed/26393648)

A 60-Year-Old Woman Comes to the Office with Intermittent Flatulence