Urea( urea nitrogen) in serum

Urea is the end product of protein metabolism in the body. It is removed from the body by glomerular filtration, 40-50% of it is reabsorbed by the tubular epithelium of the kidneys and is actively secreted by tubular cells. In pathology, the shifts in urea concentration in the blood depend on the ratio of the processes of its formation and excretion. The reference values ​​for the urea concentration( of urea nitrogen ) in the blood serum are given in the table.

Reference values ​​for urea( urea nitrogen) in the blood serum

Reference values ​​for urea( urea nitrogen) in serum

Reduced urea concentration in blooddoes not have special diagnostic value, it is possible after the introduction of glucose, with reduced protein catabolism, increased diuresis, after hemodialysis( for example, during poisoning), fasting,in liver failure.

There are three groups of causes leading to an increase in the concentration of urea in the blood: adrenal, renal and adrenal azotemia.

■ Adrenal azotemia is also called production azotemia, because it is caused by increased formation of nitrogenous slags in the body. This type of azotemia is observed when consuming a very large amount of protein food, various inflammatory processes with marked increase in protein catabolism, dehydration as a result of vomiting, diarrhea, etc. Under these conditions, excess urea is rapidly removed from the body by the kidneys. A prolonged increase in the urea concentration in the serum above 8.3 mmol / l should be regarded as a manifestation of renal insufficiency.

■ Increased urea concentration in the blood most often occurs as a result of impaired renal excretory function. Renal( retentional) azotemia can cause the following forms of pathology.

□ Acute and chronic glomerulonephritis;in acute glomeruli-nephritis, an increase in urea concentration occurs rarely and, as a rule, it is short-lived;in chronic glomerulonephritis, the urea content may fluctuate, increasing with an aggravation of the process and decreasing with its attenuation.

□ Chronic pyelonephritis;the increase in urea concentration in these patients depends on the severity of nephrosclerosis and the inflammatory process in the kidneys.

□ Nephrosclerosis caused by poisoning with mercury salts, glycols, dichloroethane, other toxic substances.

□ Syndrome of prolonged compression( crushing);the concentration of urea in the blood is very high, which is due to the combination of delayed excretion of urea with increased protein breakdown.

□ Arterial hypertension with malignant course.

□ Hydronephrosis, expressed polycystosis, kidney tuberculosis.

□ Amyloid or amyloid-lipoid nephrosis;the increase in urea in the blood in these patients is observed only in the late stages of the disease.

□ Acute renal failure( ARF);the concentration of blood urea often reaches very high values ​​- 133.2-149.8 mmol / l. Of great importance is the magnitude of the increase in the level of urea in patients with acute renal failure. So, in uncomplicated cases, the urea concentration in the blood increases by 5-10 mmol / l / day, and in the presence of infection or extensive trauma it rises by 25 mmol / l / day.

■ Adrenal azotemia refers to retinal azotemia and occurs when urinary retention is obstructed by obstructions in the urinary tract( stone, tumor, particularly adenoma or prostate cancer).