section name header

Introduction ⬇

Amylase is an enzyme that changes starch to sugar. It is produced in the salivary glands, pancreas, liver, and fallopian tubes and is normally excreted in small amounts in the urine. If the pancreas or salivary glands are inflamed, much more of the enzyme enters the blood, and consequently, more amylase is excreted in the urine.

This test of blood and urine indicates pancreatic function and is done to differentiate acute pancreatitis from other causes of abdominal pain, epigastric discomfort, or nausea and vomiting.

In patients with acute pancreatitis, the urine often shows a prolonged elevation of amylase, compared with a short-lived peak in the blood. Moreover, urine amylase may be elevated when blood amylase is within normal range, and, conversely, the blood amylase may be elevated when the urine amylase is within normal range. The advantage of the amylase-creatinine clearance test is that it can be done on a single random urine specimen and a single serum sample instead of having to wait for a 2- or 24-hour urine collection. The ratio is increased in certain conditions other than acute pancreatitis, such as diabetic acidosis and renal insufficiency. Although the usefulness of this test in pancreatic disease has been questioned, it can be helpful to screen for macroamylasemia.

Normal Findings ⬆ ⬇

Amylase/Creatinine Clearance Ratio

1%–4% or 0.01–0.04 clearance fraction. This is a ratio calculated as follows:

Urine Amylase

2-hour specimen: 2–34 U or 16–283 nkat/hr

24-hour specimen: 24–408 U or 400–6800 nkat/d

Values vary according to laboratory methods used. Check with your lab.

Procedure ⬆ ⬇

For the amylase clearance test, a venous blood sample of 4 mL must be collected at the same time the random urine specimen is obtained.

  1. Order a random, 2-hour, or 24-hour timed urine specimen. A 2-hour specimen is usually collected.

  2. Refrigerate the urine specimen. Amylase is unstable in acidic urine. The pH must be adjusted to pH >7.0.

  3. Follow general instructions for the appropriate urine collection.

  4. Record exact starting and ending times on the specimen container and on the healthcare record. This is very important for calculation of results.

  5. Send the specimen to the laboratory.

Clinical Implications ⬆ ⬇

  1. Amylase/creatinine clearance is increased in:

    1. Pancreatitis, pancreatic cancer

    2. Diabetic ketoacidosis (some patients)

    3. Toxemia of pregnancy, hyperemesis of pregnancy

    4. Renal insufficiency

  2. Amylase/creatinine clearance is decreased in macroamylasemia.

  3. Urine amylase is increased in:

    1. Pancreatitis

    2. Parotitis

    3. Intestinal obstruction

    4. Diabetic ketoacidosis

    5. Strangulated bowel

    6. Pancreatic cyst

    7. Peritonitis

    8. Biliary tract disease

    9. Some lung and ovarian tumors

  4. Urine amylase is decreased in:

    1. Pancreatic insufficiency

    2. Advanced cystic fibrosis

    3. Severe liver disease

    4. Acute kidney injury

    5. Macroamylasemia

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain purpose of test, procedure for urine collection, and interfering factors. Written instructions can be helpful.

  2. Encourage fluids if they are not restricted.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Monitor appropriately.

  2. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

Follow-up calcium levels should be checked in fulminating pancreatitis because extremely low calcium levels can occur

Interfering Factors ⬆

  1. Acid pH decreases urine amylase.

  2. Some drugs produce increased amylase and possible pancreatitis.