Causes of an increase and decrease in amylase

In acute pancreatitis, the blood and urine amylase rises by a factor of 10-30. Hyperamilazemia occurs at the onset of the disease (after 4-6 hours), reaches a maximum after 12-24 hours, then rapidly decreases and comes to normal on the 2-6th day. The level of increase in serum amylase activity does not correlate with the severity of pancreatitis.

The activity of amylase in the urine begins to increase 6-10 hours after an acute attack of pancreatitis and returns to normal after 3 days. In some cases, the activity of amylase in the urine has two increase waves for 3 days. The diagnostic sensitivity of the determination of amylase in serum for acute pancreatitis is 95%, specificity is 88%.

Acute pancreatitis can occur without increasing the activity of amylase (in particular, with pancreatonecrosis). In the first day after the onset of the disease, a normal level of urine amylase activity is detected in 25% of patients with abortive pancreatitis, 20% with fat, and 10% with hemorrhagic. More accurate information is obtained by studying the activity of amylase in the daily volume of urine. An important and, in some cases, crucial for the recognition of the recurrent form of acute pancreatitis is a repeated increase in the activity of blood and urine amylase during recurring recurrences of the pain syndrome. In various forms of acute pancreatitis, the dynamics of increase in alpha amylase in blood and urine is of a different nature. So, for edematous pancreatitis, short-term amylase is characteristic for 1-3 days of the disease; for fatty pancreonecrosis - high and long amylase, and for hemorrhagic pancreatic necrosis - short-term hyperamilazemia on the 3rd day of the disease. Pathogenetically, hyperamilazemia develops as a result of blockade by the edematous interstitial tissue of the excretory ducts of the pancreas and is most typical for fat pancreatonecrosis. With hemorrhagic pancreatic necrosis, a sharp increase in the activity of α-amylase in the blood is noted, followed by a rapid decrease in it, which reflects the progression of necrosis.

Hyperamilazemia and hyperamilazuria are important, but not specific for acute pancreatitis; in addition, the increase in their activity may be short-lived. To increase the informativeness of the obtained results of the study, it is useful to combine the activity of blood and urine amylase with a parallel determination of the creatinine concentration in urine and serum. Based on these data, the index of amylase-creatinine clearance is calculated by the following formula:

[(AM × CrC) / (CrM × AC)] × 100,

Where AM - amylase of urine; AC - amylase of blood serum; KrM - creatinine in urine; KrS - serum creatinine.

Normally, the amylase-creatinine index is no more than 3, its increase is considered a sign of pancreatitis, as pancreatitis increases the level of true pancreatic amylase, and its clearance is 80% faster than the clearance of saliva amylase. Nevertheless, it is established that in acute pancreatitis the clearance of both beta and S-amylases increases significantly, which is explained as follows. In healthy people, the serum amylase is first filtered in the renal glomeruli, and then reabsorbed by tubular epithelium. In acute pancreatitis, tubular reabsorption is inhibited by excessive excretion of beta and S-amylase. Since the amylase activity of the serum in acute pancreatitis is mainly due to beta-amylase, the clearance of beta-amylase increases with an increase in the clearance of total amylase. In acute pancreatitis, the activity of serum amylase and the amylase-creatinine clearance is usually increased by suppressing the renal tubular reabsorption of amylase. In diseases under the guise of pancreatitis, serum amylase activity may increase, but the amylase-creatinine clearance remains normal, since there is no tubular defect. It is very important for this study to collect blood and urine at the same time.

In chronic pancreatitis, the activity of amylase in the blood and urine increases (in 10-88% and 21-70% of patients, respectively) during the process exacerbation and when there are obstacles to outflow of pancreatic juice (inflammation, edema of the pancreas head and compression of ducts, scar stenosis of the papilla duodenum, etc.). In the sclerotic form of pancreatitis, hyperamilazemia is also determined by the degree of impaired ductility and the functional capacity of the remaining part of the gland. To increase the sensitivity of the study of the activity of blood and urine amylase in chronic pancreatitis, A.I. Khazanov (1997) recommends that they be analyzed on the first day of their stay in the hospital, then at least two times after instrumental research (fibrogastroduodenoscopy, X-ray examination of the stomach and intestines, etc.), as well as at the time of pain in the abdomen. At the same time, the sensitivity of the test rises from 40 to 75-85%.

In chronic pancreatitis with fibrotic changes in the pancreas, exacerbations, often expressed and common, are accompanied by a relatively small increase in the activity of amylase.

Due to a violation of the functional capacity of the pancreas, hyperamylasemia can often be absent in acute purulent pancreatitis (with extensive "total" pancreatic necrosis necrosis).

In pancreatic cancer, the activity of amylase in the blood and urine may increase, but often remains within normal limits or even decreases.

Evaluation of the results of the study of the activity of amylase in blood and urine is complicated by the fact that the enzyme is also contained in salivary glands, large intestine, skeletal muscles, kidneys, lungs, ovaries, fallopian tubes, prostate gland. Therefore, the activity of amylase can be increased in a number of diseases having a similar pattern with acute pancreatitis: acute appendicitis, peritonitis, perforated ulcer of the stomach and duodenum, intestinal obstruction, cholecystitis, mesenteric vascular thrombosis, as well as pheochromocytoma, diabetic acidosis, for heart defects, after liver resection, for taking large doses of alcohol, for taking sulfonamides, for morphine, for thiazide diuretics, for oral contraceptives. The increase in amylase activity in these diseases is due to a number of reasons and is reactive in most cases. Due to the large reserves of amylase in acinar cells, any violation of their integrity or the slightest difficulty in the outflow of the secretion of the pancreas can lead to a significant ingress of amylase into the blood. In patients with peritonitis, an increase in amylase activity may reflect the multiplication of amylase-forming bacteria. Typically, the activity of alpha amylase in these diseases increases in blood 3-5 times.

Reduction of alpha-amylase activity in the blood is possible with thyrotoxicosis, myocardial infarction, pancreatic necrosis.

[1], [2], [3], [4], [5], [6], [7]