Urea

Urea is a waste product of protein metabolism that forms in the dog’s body and is excreted mainly via the kidneys with the urine. The urea level in the blood is considered an important indicator of kidney function and provides clues about kidney diseases or other health problems.

What is urea?

Urea is formed in liver metabolism during the breakdown of proteins. Ammonia, a substance toxic to the body, is released in the process. The liver converts the ammonia into urea, which is transported via the blood to the kidneys and excreted there with the urine. The urea level in the blood is also referred to as blood urea level or BUN (Blood Urea Nitrogen).

Significance of urea in the body

Urea is a normal component of metabolism. It ensures that excess nitrogen is safely removed from the body. Because excretion occurs via the kidneys, the blood urea level reflects both kidney function and the dog’s protein intake. A normal value indicates that the kidneys are working correctly and protein metabolism is in balance.

When is the urea level measured?

The vet measures the urea level if there is suspicion of kidney problems or liver diseases, as well as for a general check of the metabolic status. Typical occasions are:

• Kidney diseases: Elevated urea levels can be an indication of kidney failure or impaired kidney function. Since urea is excreted via the kidneys, reduced kidney performance leads to a rise in the blood urea level.
• Dehydration: In cases of dehydration, the urea level can rise because the kidneys filter less blood and thus excrete less urea.
• Nutrition-related problems: A protein content that is too high in the diet can increase the urea level. Conversely, a protein deficiency can lead to a low urea level.
• Liver diseases: The liver is responsible for urea production. If it does not function properly, the urea level may fall.
• Urinary tract infections or blockages: Problems in the urinary tract, such as urinary tract infections or blockages, can lead to an accumulation of urea in the blood because urine cannot be excreted properly.

Causes for elevated urea levels

An elevated urea level often indicates impaired kidney function or other health issues. The most common causes:

1. Chronic or acute kidney failure: When the kidneys do not function properly, they cannot effectively filter urea from the blood, causing levels to rise. Chronic kidney diseases are relatively common in older dogs.
2. Dehydration: In cases of drying out, fluid balance is disturbed, which impairs kidney performance and increases urea levels.
3. High protein intake: A protein-rich diet or the breakdown of body tissue in severe illnesses increases urea production and thus blood urea levels.
4. Heart failure: In cases of heart disease, blood flow to the kidneys may be restricted, reducing urea excretion and increasing blood levels.
5. Urinary tract blockages: A blockage in the urinary tract, for example due to stones or tumours, hinders normal urine flow and leads to a backflow of urea into the blood.

Causes of low urea levels

A low urea level can also indicate health problems, particularly in connection with protein metabolism or liver function:

1. Liver diseases: The liver produces urea. If it is damaged by a liver disease, urea production may decrease.
2. Protein deficiency: A nutrition with too little protein can lower urea levels, as less nitrogen is broken down.
3. Excessive fluid loss: In cases of polyuria (excessive urination) or diabetes insipidus, blood urea levels may be low because it is excreted more quickly.

Diagnosis through urea measurement

Urea measurement is carried out via a blood test, usually as part of a blood chemistry test. In combination with the creatinine level, the vet can specifically assess kidney function. Additionally, a urine test may be useful to evaluate the excretion of urea and other waste products.

1. Blood test: The vet takes a blood sample and measures the blood urea level (BUN). The value provides insight into how much urea is present in the blood and allows conclusions to be drawn about kidney function and protein metabolism.
2. Creatinine: The creatinine level is often measured together with urea. Elevated creatinine levels in conjunction with elevated urea indicate kidney diseases.
3. Urine analysis: A urine sample can help evaluate urea excretion and uncover possible problems with kidney filtration.

Treatment of abnormal urea levels

Treatment depends on the respective cause:

Elevated urea levels:

• In cases of elevated urea levels due to kidney diseases, a dietary adjustment may be advisable. Special renal diets with reduced protein and phosphorus content can support kidney function.
• Fluid therapy is used in cases of dehydration or to support kidney function.
• In cases of heart problems or urinary tract blockages, specific drug treatment may be necessary.

Low urea levels:

• Low urea levels due to liver diseases require treatment that supports liver function, for example with hepatic diets or specific medications.
• In cases of nutritional causes, a protein substitute through balanced nutrition can help.

Urea at a glance

Urea is a central marker for kidney function and protein metabolism in dogs. Both elevated and low levels can indicate serious illnesses, from kidney problems to liver damage and dehydration. Regular monitoring of urea levels is worthwhile, especially in older dogs or animals with known pre-existing conditions, so that the vet can act early.