The patient has a clear history of chemotherapy-induced severe acute pancreatitis, well-illustrated by the sudden onset of severe abdominal pain just after receiving L-asparaginase, which is a common drug used in ALL treatment protocols and is known to produce acute pancreatitis, characterized by epigastric pain radiating to the back, with nausea, vomiting, and abdominal distension. Most patients with severe acute pancreatitis have such pain, and approximately 90% have associated nausea and vomiting.
The patient's episode of pancreatitis was severe and most likely hemorrhagic because she developed Cullen sign (periumbilical ecchymosis) and became hemodynamically unstable, requiring admission to the ICU, transfusions, and parenteral nutrition. Breakdown of pancreatic tissue allows spillage of digestive enzymes into the retroperitoneum; this, in turn, produces severe inflammation that affects vascular structures, leading to hemorrhage and necrosis.
An example of CT scan findings in a patient with EPI is shown in Figure 1, and an example of residual islets in dense fibrous stroma secondary to loss of exocrine pancreatic tissue in chronic pancreatitis is shown in Figure 2.
Although chronic pancreatitis is the most common cause of EPI in adults, such a severe episode of acute pancreatitis entails a grave metabolic insult to the pancreatic exocrine cells, leading to necrosis, fibrosis, and loss of function. It ensures the gradual and irreversible replacement of normal pancreatic acinar cells by inflammation and fibrosis. As scarring progresses, a concomitant decrease in the exocrine function of the acinar cells is noted.
The pancreas secretes approximately 1.5 L of enzyme-rich fluid every day for the digestion of fats, starch, and protein. The exocrine pancreas produces three main types of enzymes: amylase, protease, and lipase. Lipase breaks undigested triglycerides into fatty acids and monoglycerides, which are then solubilized by bile salts. Whereas protein and carbohydrate undergo initial digestion in the stomach, triglycerides remain mostly unchanged until they reach the small intestine. Intragastric breakdown accounts for approximately 10% of total lipid digestion.
Pancreatic secretion is controlled by hormonal and neuronal mechanisms. The principal regulatory hormones are secretin and cholecystokinin (CCK). Both are tightly regulated by negative feedback mechanisms. Secretin is secreted in response to acid in the duodenum, causing duct cells to release water and bicarbonate; CCK is secreted from gut endocrine cells in response to the presence of protein and fat in the proximal intestine, acting directly and through vagal afferents to stimulate pancreatic acinar cells to release digestive proenzymes.
Pancreatic function tests (PFTs) are classified as direct or indirect. Direct PFTs involve the stimulation of the pancreas through the administration of a meal or hormonal secretagogues, after which duodenal fluid is collected and analyzed to quantify normal pancreatic secretory content (enzymes and bicarbonate). Only a few specialized centers perform these tests. Indirect tests measure the consequences of pancreatic insufficiency and are more widely available. However, direct PFTs are more sensitive and specific measures for pancreatic insufficiency.
Although several indirect tests have been developed, they depend on the consequences of pancreatic maldigestion, which are generally not apparent until normal enzyme secretory output has declined by more than 90%. Thus, they are insensitive for early pancreatic insufficiency. Their main role is in the evaluation of fat malabsorption. Fecal tests are most commonly used to evaluate children, in which direct tests are highly impractical. The fecal elastase test is preferred in most centers in the United States.
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Cite this: Jaime Shalkow, Mayela E. García. A 15-Year-Old Girl With Steatorrhea Who Can’t See at Night - Medscape - Nov 13, 2019.