2015年8月21日星期五

A Brief Introduction of Urea Nitrogen

Urea concentration is measured as urea nitrogen. Measurement of urea nitrogen in serum can be used to screen for decreased GFR, and the test is often called blood urea nitrogen (BUN).

Urea is an organic chemical compound, and is essentially the waste produced by the body metabolizing protein. Naturally, the compound is produced when the liver breaks down protein or amino acids, and ammonia; the kidneys then transfer the urea from the blood to the urine. Excess nitrogen is excreted from the body through urea.

Urea nitrogen concentrations depends on:

1. Hepatic urea production

The urea production rate depends on hepatic function and digestion and catabolism of protein. In liver disease, for example, urea formation is decreased. While, urea formation increases with protein catabolism or increased protein digestion in the intestine.

2. Renal tubular flow rate

Urea can be filtered through the glomerulus and passively diffuses out of the tubules at a rate depending on renal tubular flow rate; the remainder of the filtered urea is expelled in urine. About 40% of filtered urea can be reabsorbed at high flow rate; at low flow rate, around 60% of filtered urea is reabsorbed and added back to the urea concentration of blood. Therefore, high UN levels can be seen with reduced GFR.

Increased urea nitrogen may appear due to factors including:

▪ Increased catabolism of protein: Fever, burns, corticosteroid administration, starvation, physical activity.

▪ Increase of protein digestion: high-protein diet, and hemorrhage into the gastrointestinal system.

▪ Reduced GFR: pre-renal, renal or post-renal causes.

Decreased urea nitrogen may occur due to reasons like:

▪ Decrease of protein intake or protein anabolism: limit of protein intake.

▪ Increased excretion: any cause of polyuria, such as Diabetes, hyperadrenocorticism.

▪ Decreased production: liver disease.


The above-mentioned is about introduction of urea nitrogen. If there is still any questions, feel free to consult our online experts.

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