Children with pancreatic exocrine insufficiency havemany bulky, foul-smelling stools each day, usually withvisible oil or fat. They typically have voracious appetitesbecause of massive malabsorption of calories from fat,complex carbohydrates, and proteins. Failure to thrive isuniformly present if diagnosis and treatment are not accomplished rapidly. It is important to distinguish children withmalabsorption due to pancreatic disease from children withintestinal disorders that interfere with digestion or absorption. Appropriate testing should be performed to rule outconditions such as celiac disease and inflammatory boweldisease if any doubt about the state of pancreatic sufficiencyexists.
Testing of pancreatic function is difficult. Direct measurement of enzyme concentrations in aspirated pancreatic juice is not routine and is technically difficult. Stools can be tested for the presence of maldigested fat, which usually indicates poor fat digestion. Measuring fecal fat can give either a qualitative assessment of fat absorption (fecal Sudan stain) or a semiquantitative measurement (72-hour fecal fat determination) of fat maldigestion. Another way to assess pancreatic function is to test for the presence of pancreatic enzymes in the stool. Of these, measuring fecal elastase-1 by immunoassay seems to be the most accurate method of assessment. Depressed fecal elastase-1 concentration correlates well with the presence of pancreatic insufficiency.
Replacement of missing pancreatic enzymes is the best available therapy. Pancreatic enzymes are available as capsules containing enteric-coated microspheres. The coating on these spheres is designed to protect the enzymes from gastric acid degradation. For children unable to swallow capsules, the contents may be sprinkled on a spoonful of soft food, such as applesauce. Excessive use of enzymes must be avoided because high doses (usually >6000 U/kg/meal) can cause colonic fibrosis. In infants, typical dosing is 2000 to 4000 U of lipase/120 mL of formula. In children younger than 4 years old, 1000 U/kg/meal is given. For older children, 500 U/kg/meal is usual. This dose may be adjusted upward as required to control steatorrhea, but a dose of 2500 U/kg/meal should not be exceeded. Use of H2 receptor antagonists or proton-pump inhibitors can increase the efficacy of pancreatic enzymes by enhancing their release from the microspheres and reducing inactivation by acid.
The exocrine pancreas produces numerous proteolyticenzymes, including trypsin, chymotrypsin, and carboxypeptidase. These are produced as inactive proenzymes to protectthe pancreas from autodigestion. Trypsin is activated after leaving the pancreas by enterokinase, an intestinal brush border enzyme. After activation, trypsin cleaves other proteolytic proenzymes into their active states. Protease inhibitorsfound in pancreatic juice inhibit early activation of trypsin;the presence of self-digestion sites on the trypsin moleculeallows for feedback inactivation. Pancreatitis occurs when digestive enzymes are activated inside the pancreas, causinginjury. Triggers for acute pancreatitis differ between adultsand children. In the adult patient, most episodes are relatedto alcohol abuse or gallstones. In children, most cases areidiopathic or due to medications. Some cases are caused bypancreatic sufficient cystic fibrosis, hypertriglyceridemia,biliary microlithiasis, trauma, or viral infection. Collagenvascular disorders and parasite infestations are responsiblefor the remainder (Table 131-1).
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