Urea
Urea is the final product of protein breakdown in the body. When excreted through the kidneys, the residues of "unnecessary" nitrogen are removed. It is formed in the liver and is excreted together with urine and partially with sweat (which gives sweat a specific smell). Urea helps the body retain water and some trace elements. This is done by reabsorption by the kidneys into the bloodstream. Every time the absorption process takes place, urea "pulls" water and mineral molecules back into the bloodstream. However, its excessive content harms organs and tissues.
The level of urea depends on the balance of its formation and removal from the body. A decrease in concentration is possible with a low-protein diet or starvation, liver disease, poisoning with chemicals (arsenic, phosphorus-containing compounds), during pregnancy, or after hemodialysis. In clinical practice, an increase in urea content (azotemia) is of the greatest importance, which happens for 3 main reasons:
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Production (adrenal) azotemia: It is characterized by excessive formation of toxins, which is possible with:
- excessive protein content in food (meat, beans, liver, soy);
- dehydration;
- inflammatory diseases with increased destruction of proteins.
In these cases, urea is rapidly excreted by the kidneys, but if the concentration is over 8.3 mmol/l for a long time, then this is regarded as a manifestation of renal insufficiency.
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Renal azotemia: It occurs due to kidney diseases, which cannot cope with their function of excreting urea from the body. Possible diseases include:
- pyelonephritis,
- glomerulonephritis,
- hydronephrosis,
- amyloidosis of the kidneys,
- acute kidney failure.
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Subrenal azotemia: The reason is a mechanical obstacle to the excretion of urea through the urinary system (it begins to be absorbed back into the blood), which is due to:
- stones,
- tumors (prostate adenoma).