A 55-year-old man with a history of chronic pancreatitis and alcohol abuse is investigated for recent onset weight loss, decreased appetite, and worsening of chronic abdominal pain. Physical examination is significant for diffuse muscle atrophy, temporal wasting, and a mildly enlarged liver without ascites. Serum lipase and amylase are normal, and aspartate aminotransferase (AST) is mildly elevated. Abdominal imaging shows a malignant mass in the pancreas. The patient subsequently undergoes an uncomplicated subtotal pancreatectomy and returns for a postoperative nutritional assessment following hospital discharge. Which of the following tests will most likely be normal in this patient after surgery?

Question

A 55-year-old man with a history of chronic pancreatitis and alcohol abuse is investigated for recent onset weight loss, decreased appetite, and worsening of chronic abdominal pain.  Physical examination is significant for diffuse muscle atrophy, temporal wasting, and a mildly enlarged liver without ascites.  Serum lipase and amylase are normal, and aspartate aminotransferase (AST) is mildly elevated.  Abdominal imaging shows a malignant mass in the pancreas.  The patient subsequently undergoes an uncomplicated subtotal pancreatectomy and returns for a postoperative nutritional assessment following hospital discharge.  Which of the following tests will most likely be normal in this patient after surgery?

Quizplus · Accepted Answer

The exocrine pancreas has a significant secretory reserve, and >90% of the glandular tissue must be destroyed before a patient will develop clinical malabsorption. However, this patient likely has significant loss of pancreatic tissue at baseline due to chronic pancreatitis and is at increased risk for exocrine insufficiency. Following partial pancreatic resection, he may develop clinically significant deficiency in any of the pancreatic digestive enzymes normally secreted into the duodenum. Pancreatic amylases, along with salivary and brush border amylases, are required for the degradation of polysaccharides into monosaccharides, as polysaccharides cannot be absorbed by the intestinal mucosa. In contrast, monosaccharides (eg, glucose, galactose) are taken up directly by the epithelial cells of the small intestine through either sodium-dependent cotransport or facilitated diffusion. D-xylose is a monosaccharide that is absorbed directly without the action of pancreatic enzymes, and can be used to test for brush border absorptive function independent of pancreatic function. Intestinal D-xylose absorption can also decrease with bacterial overgrowth of the small intestine. (Choices A and B) Patients with exocrine pancreatic insufficiency will have decreased secretion of trypsin and lipase into the duodenum following cholecystokinin (CCK) stimulation. (Choice D) Trypsinogen is a proenzyme secreted by the exocrine pancreas into the small intestine. Small quantities are also detectable in serum. Serum trypsinogen levels are increased in acute pancreatitis but often decreased in patients with chronic pancreatitis or other forms of chronic pancreatic insufficiency. (Choice E) The stool neutral fat (triglyceride) content is increased after pancreatic resection due to deficiency of pancreatic lipase. Educational objective: Polysaccharides must be degraded to monosaccharides by pancreatic and brush border amylases before they can be absorbed. Monosaccharides can be absorbed directly. D-xylose is a monosaccharide whose absorption is not affected by exocrine pancreatic insufficiency, and can be used to differentiate between pancreatic versus mucosal causes of malabsorption.

A 55-Year-Old Man with a History of Chronic Pancreatitis and Alcohol