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Hyperamylasemia

Causes of Hyperamylasemia
The amylase enzyme is found in many organs besides the pancreas (salivary glands, liver, small intestine, kidney, fallopian tubes) and can be produced by various tumors (carcinoma of lung, esophagus, breast, and ovary). No blood test is reliable for the diagnosis of acute pancreatitis in patients with renal failure. The serum amylase can become elevated when the creatinine clearance is less than 50 ml/min.

Pancreatic Disease

  1. Acute pancreatitis
  2. Pancreatic pseudocyst
  3. Pancreatic trauma
  4. Pancreatic carcinoma

Nonpancreatic Disease

  1. Renal insufficiency
  2. Salivary gland lesions
  3. Tumor (lung, esophagus, * ovary, breast)
  4. Diabetic ketoacidosis *
  5. Burns
  6. Pregnancy
  7. Renal transplantation
  8. Drugs (morphine, codeine)
  9. Macroamylasemia
    Normal serum lipase & urine amylase.  Amylase-creatinine clearance ration < 1% with normal renal function.
  10. Other Abdominal Disorders
  11. Biliary tract disease (cholecystitis, choledocholithiasis)
  12. Perforated peptic ulcer
  13. Intestinal obstruction or infarction
  14. Postoperative hyperamylasemia
  15. Peritonitis
  16. Ruptured ectopic pregnancy

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*Salivary isoamylase elevated and not pancreatic isoamylase.

REF: Noble: Textbook of Primary Care Medicine, 3rd ed., 2001 Mosby, Inc.

The most important thing to remember is that the patient with asymptomatic, chronic hyperamylasemia almost never has pancreatic disease as the cause of the amylase elevation.

In cases of mild elevations of serum amylase, other methods may be used to help determine the cause of hyperamylasemia:

The amylase-to-creatinine clearance ratio (ACR) can help differentiate acute pancreatitis from other conditions.

ACR = (amylase [urine] x creatinine [serum]) / (amylase [serum] x creatinine [urine]) X 100

An ACR greater than 5% suggests acute pancreatitis. However, the ACR also is known to be increased in diabetic ketoacidosis, surgery, and renal disease. An ACR less than 1% suggests macroamylasemia.

Because urinary amylase is relatively nonspecific, calculations for urinary amylase excretion have almost no clinical value. Generally, ACR measurement has been abandoned, except to confirm a diagnosis of macroamylasemia, which is characterized by low ACR.

The lipase/amylase ratio. A lipase/amylase ratio of greater than 2 suggests alcoholic pancreatitis. This has been shown in studies not to be a reliable predictor of alcoholic pancreatitis.

Serum isoamylase measurements to determine S-type, P-type, or macroamylasemia. This is the best test to use when the etiology of hyperamylasemia is obscure.

Ref:  iMedicine 2002

         

03192002