Urine amylase

Sample for Urine amylase

1. The sample is urine.
2. Can obtain random 2 hours urine sample.
3. Amylase is unstable in acidic urine, so adjust pH to the alkaline range.
4. Store urine at 4 °C.
   1. Or can collect 24-hour samples. Discard the first sample and then collect the rest of the 24-hour sample in the container, including the last sample.
5. Also, collect venous blood to make the serum for the serum amylase level.
6. For blood tests, don’t eat or drink for at least 2 hours.

Precautions for Urine amylase

1. Urine amylase is unstable in acidic urine. Acid urine decreases amylase levels.
2. Adjust the pH to  7.0.
3. Refrigerate the urine.
4. Avoid urine contamination by stool.

Purpose of the test (Indications) for urine Amylase

1. This test tells about pancreatic dysfunction.
2. It differentiates acute pancreatitis from other:
   1. Abdominal pain.
   2. Epigastric discomfort.
   3. Nausea and vomiting.
3. It diagnoses pancreatitis in the late stages when the blood amylase is normal.
4. Raised in acute pancreatitis, cholelithiasis, and peptic ulcer.

Precautions for amylase

1. Urine contaminated with feces.
2. Medications that increase the result are dexamethasone, furosemide, methanol, ethanol, thiazide, salicylates, chloride salts, and meperidine.
3. Medication that will decrease the level is citrate.

Definition of amylase

1. The amylase enzyme changes starch to sugar.
2. Amylase is described into two forms:
   1. α-Amylase found in humans.
   2. β-Amylase is found in plants and bacteria.

The action of the amylase

1. Amylase enzymes change starch into sugars.
2. Large polysaccharide molecules are broken into smaller units of dextrin, maltose, and glucose.
3. Salivary glands have the greatest concentration, and they will convert starch into sugars (Hydrolysis of starch) while food is in the mouth and esophagus.
4. Normally a low level of amylase is found in the blood and excreted in a small amount in the urine.
5. When the pancreas and salivary glands are inflamed, much more enzyme enters the blood, and as a result, more amylase is excreted in the urine.
6. In the case of pancreatitis, amylase level is raised in the blood for a short time, while in the urine remains for several days.

The site of formation of amylase:

1. Salivary glands. These glands have the greatest concentration.
2. Pancreas.
3. Liver (little or no amylase activity).
4. Fallopian tubes.

Amylase activity is also found in:

1. Semen, testes.
2. Ovaries, fallopian tubes.
3. Striated muscles.
4. Lungs.
5. Adipose tissue.
6. Colostrum and milk.
7. The tears.

Secretion of amylase:

1. Amylase from pancreatic acini goes through the pancreatic duct into the duodenum.

2. Once in the intestine, it converts carbohydrates into simple sugars.
3. Amylase activity in the serum and urine is of pancreatic and salivary glands origin.

Excretion of amylase:

1. An Amylase is a small unit, and it can pass through the glomeruli and is found in the urine.
2. Urinary amylase clearance is increased in acute pancreatitis from normal to 3 folds.
3. A value of >550 U/L has a sensitivity of 62% and 97%, specific for acute pancreatitis.
4. In damage to the salivary glands or pancreas, more enzyme in the blood is excreted in the urine.

In pancreatitis:

1. A prolonged raised level of amylase in urine may be raised until 5 to 7 days.
2. The short-lived peak in blood, maybe 1 to 2 days, and return to normal.
3. In acute pancreatitis, the Amylase picture is as follows:
   1. The initial rise of 2 to 12 hours.
   2. The peak level is 12 to 72 hours.
   3. The normal level reaches 3 to 4 days (short-lived peak).
   4. Urine amylase may remain elevated up to 2 weeks after the acute episode of acute pancreatitis.

Amylase/creatinine clearance ratio:

Principle of amylase/creatinine clearance ratio:

1. Amylase excretion in the urine depends upon renal function, so urinary excretion of amylase correlates with creatinine clearance.
2. In acute pancreatitis, there is increased clearance of amylase in the urine compared to creatinine.
3. Amylase/creatinine clearance ratio depends upon this function of the kidneys.

Advantages of amylase/creatinine clearance ratio:

1. This is done on a single random urine sample and a single serum sample instead of 2 hours or 24 hours.
2. The calculation of the amylase/creatine clearance ratio normally is 1% to 4%.
3. Amylase/creatinine clearance ratio becomes abnormal after 1 to 2 days of the serum amylase level, and it will remain abnormal as long as urine amylase is present.
4. Amylase/creatinine clearance ratio is more accurate than the serum amylase.

Disadvantages of amylase/creatinine clearance ratio:

1. The exact degree of specificity is still not established.
2. This may be raised in some cases of diabetic ketoacidosis and burns.
3. In mild azotemia, this may be normal, but severe azotemia is raised.
4. Some author believes that this has little value.

Normal Urine Amylase 

Source 1

• 1 to 17 U/hour
• 170 to 2000 U/L
• Abbott TDX =  5 to 27 U/h.

Source 2

• Up to 5000 Somogyi units /24 hours Or
• 6.5 to 48.1 units/hour.

Sources 4

• 2 hours sample           = 2 to 34 U
• 24-hour sample         = 24 to 408 U.
  • Another reference gives a normal range = 1 to 17 U/h.
• So different kits have a different ranges.

Another source

• <400 IU/L

Another source

• 0 to 275 units/L

Increase urine Amylase level seen in:

1. Acute Pancreatitis.
2. Chronic relapsing pancreatitis.
3. Penetrating peptic ulcer to the pancreas.
4. Intestinal obstruction.
5. Acute cholecystitis.
6. Parotitis (mumps) is called sialadenitis.
7. Ruptured ectopic pregnancy.
8. Pulmonary infarction.
9. Autoimmune diseases.
10. Pancreatic cyst.
11. Peritonitis.
12. Biliary tract disease.
13. Diabetic ketoacidosis.
14. Intestinal obstruction.
15. Few lung or ovarian tumors.
16. Alcoholic intoxication.
17. Diabetic ketoacidosis.
18. Acute respiratory insufficiency.

Decreased urine Amylase is seen in:

1. Pancreatic Insufficiency.
2. Advanced chronic pancreatitis.
3. Renal failure.
4. Liver disease (severe).
5. Liver cancer.
6. Advanced cystic fibrosis.
7. Hyperglycemia.

Amylase/creatinine clearance ratio is increased in the:

1. Pancreatitis.
2. Toxemia of pregnancy.
3. Diabetic ketoacidosis.
4. Renal insufficiency.

Normal urine picture:

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