Amylase

Work-up for abdominal pain, epigastric tenderness, nausea, and vomiting. Such findings characterize acute pancreatitis as well as acute surgical emergencies such as gastrointestinal perforation (eg, peptic ulcer with perforation) or bowel infarct. Amylase is used in the differential diagnosis of acute or chronic pancreatitis, which may or may not in an individual be related to alcoholism. Hypercalcemia related to pancreatitis is described with hyperparathyroidism and other entities. About 80% of subjects with acute pancreatitis have increased serum amylase within 24 hours.¹

Poor specificity. Oxalate or citrate depress results. Lipemic sera (hypertriglyceridemia) may contain inhibitors which falsely depress results. About 20% of patients with acute pancreatitis have abnormal lipids. Normal serum amylase may occur in pancreatitis, especially relapsing and chronic pancreatitis. (Subjects in whom pseudocysts complicate chronic pancreatitis often do have elevations of the pancreatic enzymes.) The entire pancreas can be destroyed in pancreatitis; in such cases serum amylase will derive from other structures (eg, the salivary glands). Urine amylase increases often persist longer than do those of serum. High levels in alcoholics, in pregnancy and in diabetic ketoacidosis are of salivary rather than pancreatic origin. Salivary type amylase makes up about 60% of the enzyme, while it is the pancreatic fraction that is of clinical interest.² The expression “salivary amylase” includes other nonpancreatic sources of the enzyme. Serum amylase is cleared by renal excretion. Serum amylase may increase one to two times upper limit of normal in renal failure without diagnostic significance. In such cases, urine amylase is normal or low.

Enzymatic