High amylase in blood or urine

Generality

Amylases are enzymes involved in carbohydrate digestion .

They are mainly produced by pancreatic cells and salivary glands .

Pancreatic amylase splits (hydrolyzes) the ingested starch, completing its digestion in the first part of the small intestine (duodenum).

Under normal conditions, only small concentrations of amylase are found in the blood and urine. However, if there is damage to the pancreatic cells, the amount of enzymes released into the circulation is greater. For these reasons, an increase in blood and urinary concentration of amylase may be indicative of a state of inflammation and other pancreatic diseases.

What's this

Amylase (pancreatic isoenzyme) is poured into the small intestine through the pancreatic duct, where it intervenes in the digestion of carbohydrates taken with the diet.

The amylase test evaluates its presence and quantity in the blood and / or urine (representing the latter the route of excretion). These enzymes are found in higher concentrations precisely when there is damage to pancreatic cells (for example, following acute pancreatitis or recurrence from chronic inflammation) or obstruction of the pancreatic duct.

Amylase in the Blood

The concentration of amylase in the blood is called amylasemia and is determined on a simple venous blood sample; there is talk of hyperamylasemia when this concentration is too high and hypoamylasemia when this concentration is lower than normal.

Amylase in the Urine

Since the circulating amylases - by virtue of their low molecular weight - are eliminated, at least in part, with urine, their concentration in serum also depends on renal function.

The concentration of amylase in urine is called amylasuria (hyperamylasuria when it is too high, hypoamylasuria when it is lower than normal).

Why do you measure

The blood amylase test is mainly indicated to diagnose and monitor acute pancreatitis or obstruction of the pancreatic duct (due to stones or pancreatic cancer). Usually, the concentration of the enzyme in the urine mirrors that of the blood, but the increase and reduction are delayed compared to the blood.

In some cases, for example when an accumulation of fluid occurs in the abdominal cavity (ascites), the amylase test can be performed on peritoneal fluid as a support in the diagnosis of pancreatitis.

When is the exam prescribed?

The amylase test is not a routine exam. This test is prescribed by the doctor when the patient develops disorders that lead to suspicion of an alteration of the pancreas.

In general, the symptoms that indicate the presence of a pancreatic disease include:

Severe abdominal pain;
Temperature;
Loss of appetite;
Weight loss without apparent cause;
Bad digestion;
Abdominal swelling;
flatulence;
Nausea.

The amylase test can also be prescribed when chronic hepatitis has been found or after the removal of stones that have caused biliary colic.

Sometimes, amylasuria is prescribed with the determination of creatinine clearance, to evaluate the relationship between amylase and creatinine filtered by the kidneys. This test is used to investigate renal function (if reduced, this leads to a reduction in the excretion rate of amylase).

Normal values

Under normal conditions, it is possible to find a certain amount of amylase in the blood, of which about 35-40% has pancreatic origins, 55-60% comes from the salivary glands and the small remaining quota is produced by other organs, such as the small intestine, liver, lungs, placenta and fallopian tubes.

The normal amylase values are on average:

Amylase in serum: 1-225 international units per liter (IU / l);
Pancreatic fraction: 17-115 IU / l;
Salivary fraction: 17-135 IU / l;
Amylasuria: 25-1.500 IU / 24 hours.

Amylase High - Causes

Main causes of high amylases in the blood

Acute pancreatitis;
Pancreatic, ovarian or lung cancer;
macroamylasemia;
Infection of the salivary glands (such as mumps) or their obstruction;
Kidney failure;
Calculations of gallbladder or obstruction of bile ducts or pancreatic ducts;
cholecystitis;
Intestinal obstruction;
Perforated ulcer;
Viral gastroenteritis;
Ectopic pregnancy;
Cystic fibrosis.

Amylase and Pancreatitis

As said, serum and urinary amylases are important laboratory data, which help to diagnose acute and chronic pancreatitis . Increases in circulating amylases can also occur in cases of renal failure and gynecological or small bowel disorders .

PANCREATITIS (inflammation of the pancreas) is accompanied by symptoms such as severe abdominal pain, fever, loss of appetite or nausea; steatorrhea is typical in chronic forms.

During acute pancreatitis amylasemia often increases up to 4-6 times above the maximum values of the normal range. This increase occurs within 12 hours of the event and generally the plasma amylases remain high for three to four days, while the amylasuria can remain high for up to 10 days. Chronic pancreatitis is often associated with alcoholism, but can also be caused by trauma, obstruction of the pancreatic duct and various genetic diseases, such as cystic fibrosis. In the presence of chronic pancreatitis, the values of amylase in the blood can be moderately high or even normal and often diminish as the disease progresses due to the poor functionality of the organ.

Other Causes of High Amylases

By virtue of the numerous conditions which accompany it, hyperamylasemia - although having a high diagnostic sensitivity for acute pancreatitis - has a low specificity.

For this reason, it is often necessary to integrate it into the general clinical picture and into the results of other investigations. Outside of pancreatitis, blood amylase has a low diagnostic value, in the sense that the diseases and conditions that can alter its values are diagnosed without the need to control amylasemia.

Another typical condition that leads to the increase in serum amylase is the so-called macroamylase, in which these enzymes are complexed with blood globulin (proteins), forming molecular aggregates that cannot be filtered and that for this reason are not found in urine . In the presence of macroamylases the serum lipase assay can provide useful indications on a possible involvement of the pancreas.

Like amylases, lipases are also measurable and, since they are not produced by the salivary glands, they are a more specific index of pancreatic damage; Furthermore, lipasemia, after the initial phases of the pancreatic inflammatory process, tends to decrease less rapidly than amylasemia. However, the dosage of blood lipase is more difficult and it is for this reason that it is often preferred to evaluate serum amylase levels.

Laboratory investigations also make it possible to distinguish between pancreatic and salivary isoforms, thereby increasing the sensitivity and diagnostic specificity with respect to the total amylase dosage.

Blood and urine amylase concentrations can be moderately elevated in some diseases, such as: ovarian cancer, lung cancer, tubal pregnancy, acute appendicitis, diabetic ketoacidosis, mumps, intestinal obstruction or perforated ulcer.

However, the amylase test is not normally required for the diagnosis and monitoring of these diseases.

Amylase Basse - Causes

Amylasemia decreases in pancreatic insufficiency and in liver cirrhosis, while hypoamylasuria occurs in nephropathies with reduction of glomerular filtration.

A reduced blood and urinary concentration of amylases can also be indicative of permanent damage to the pancreatic producing cells. A low value may also be due to renal dysfunction or gravidase toxemia.

How to measure it

Total amylase, pancreatic amylase and lipase analysis are performed on a blood sample taken from a vein in the arm.
The analysis of amylase in the urine (amylasuria) provides, instead, the collection of a sample of urine (taken at any time of the day or within 24 hours).

Preparation

To perform the amylase blood test, it is necessary to observe a fast of at least 8 hours, during which a small amount of water can be taken.
Urine must be collected in a sterile disposable container. This can be purchased at the pharmacy or requested directly from the laboratory where the exams are to be analyzed.