Detail of the urea cycle and its regulation is the subject of a recent review [9]. A small amount This process of renal elimination, which is detailed in a recent review [10], begins with filtration of blood at the glomeruli of the approximately 1 million nephrons contained within each kidney.
During glomerular filtration, urea passes from blood to the glomerular filtrate, the fluid that is the precursor of urine. The concentration of urea in the filtrate as it is formed is similar to that in plasma so the amount of urea entering the proximal tube of the nephron from the glomerulus is determined by the glomerular filtration rate GFR.
The facility of the kidney to adjust urea reabsorption and secretion as the filtrate passes through the tubule determines an important role for urea in the production of a maximally concentrated urine, when this becomes necessary.
The mechanism of this water-conserving action of urea within the nephron is well detailed by Weiner et al [10]. Although often considered simply a metabolic waste product, urea has two important physiological functions outlined above: detoxification of ammonia and water conservation.
Around the world, essentially the same method of urea analyses is used, but the result is expressed in two quite different ways [11]. In the US and a few other countries, plasma or serum urea concentration is expressed as the amount of urea nitrogen. So the conversion factor is 0. By far the highest levels occur in the context of reduced urinary elimination of urea due to advanced renal disease and associated marked reduction in glomerular filtration rate GFR.
GFR is a parameter of prime clinical significance because it defines kidney function. All those with reduced kidney function, whatever its cause have reduced GFR and there is good correlation between GFR and severity of kidney disease. The limitation of urea as a test of renal function is that in some circumstances plasma urea is not a sufficiently accurate reflection of GFR. Furthermore, urea may be raised despite a normal GFR i. The two physiological causes are increased dietary protein and ageing.
As previously mentioned, increase in dietary protein results in increased urea production. The increased urea excretion is consequent on increased GFR, a welldocumented physiological adaptation to pregnancy. Pathological cause of reduced urea concentration is largely confined to advanced liver disease [20]. This reflects the central role that the liver plays in urea production via the urea cycle. Overhydration induces increased GFR and consequent increased excretion of urea.
Concentration in patients with renal dysfunction can range from mildly increased to severely increased, depending on severity of disease. The limitation of urea as a test of renal function relates to reduced sensitivity and specificity so that a normal urea does not necessarily exclude renal disease and a slight to moderate increase in urea cannot be assumed to be due to renal disease.
There are many non-renal causes that can be associated with such a rise and for some of these conditions, e. By comparison with urea, creatinine measurement is no more sensitive but is more specific. Under some circumstances urea may be more sensitive for detection of early renal disease than creatinine, so it has some advantage.
These issues will be explored further in a second article that will focus on the clinical value of measuring urea and creatinine together and calculating the urea: creatinine ratio.
May contain information that is not supported by performance and intended use claims of Radiometer's products. See also Legal info. Radiometer and acutecaretesting. Printed from acutecaretesting. August Urea and the clinical value of measuring blood urea concentration. The two conditions can occur at the same time. While uremia is the buildup of urea in the blood, azotemia is the buildup of nitrogen waste products in the blood. Uremia is a medical emergency that requires urgent treatment.
People with uremia may need to be hospitalized. It is not possible to treat uremia at home. Treatment focuses on the underlying cause of uremia. Blood pressure medication and medication to better control diabetes may also help. Most people with uremia will need dialysis. Some may also need a kidney transplant, which may prevent further kidney problems by replacing a diseased kidney with a healthy one.
People often have to wait many years for a kidney and may need dialysis while they wait. The symptoms of uremia are similar to those of chronic kidney disease. This similarity means that people with kidney disease who develop kidney failure may not realize they have uremia. People with kidney disease must undergo regular blood work and urinalysis to ensure their kidneys are working well. It is important to note that symptoms vary between individuals and can change, first showing improvement and then deteriorating again.
Kidney disease is a life-threatening condition, so people who suspect they have either kidney disease or uremia should see a doctor promptly. Some symptoms to watch for include:. Uremia can lead to kidney failure when left untreated. Someone with uremia may have seizures, loss of consciousness, heart attacks , and other life-threatening symptoms.
Some will need a kidney transplant. Higher than normal BUN levels can also be caused by dehydration, burns, certain medicines, a high protein diet, or other factors, including your age. BUN levels normally increase as you get older. To learn what your results mean, talk to your health care provider. Learn more about laboratory tests, reference ranges, and understanding results. A BUN test is only one type of measurement of kidney function. If your health care provider suspects you have kidney disease, additional tests may be recommended.
These may include a measurement of creatinine, which is another waste product filtered by your kidneys, and a test called a GFR Glomerular Filtration Rate , which estimates how well your kidneys are filtering blood. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.
What is a BUN blood urea nitrogen test? What is it used for? Why do I need a BUN test? This may one day also be able to slow the progression of kidney disease. The best way to try to prevent uremia if you are in end-stage renal failure is to have regular dialysis treatments. This will keep the waste filtered out of your blood.
You should also avoid eating anything high in sodium, phosphorus, and potassium. Eating a healthy diet otherwise and exercising, if approved by your doctor, can help in the prevention of uremia. Since uremia is caused by severe kidney disease and kidney failure, you can try to prevent uremia by taking steps to prevent kidney disease when possible. Some ways to prevent kidney disease include:.
There are some risk factors — like age and a family history of kidney disease — that can make it more difficult to prevent kidney disease. However, taking as many preventive measures as possible will help. The complications for uremia can be severe and, if left untreated by dialysis or transplant, can eventually lead to death. Following the treatment plan set out by your medical team can help reduce or possibly eliminate some of these complications. Uremia is a serious condition, and it can be life-threatening.
The sooner a treatment plan can be put into place, the better chance you have at preventing uremia. Azotemia occurs when your kidneys have been damaged by disease or an injury. You get it when your kidneys are no longer able to get rid of enough….
Tubes in your kidneys become damaged from a….
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