Blood Urea Nitrogen (BUN) Test.
Urea is a waste product of protein metabolism in the liver. It is carried via the blood to the kidneys where it is filtered out of the blood and then excreted in the urine.
Since protein metabolism is an ongoing process there is always a stable amount of urea nitrogen in the blood which can be measured.
What is the purpose of this test?
1. The measurement of the amount of urea nitrogen in the blood gives an idea of how well the kidneys are functioning.
2. To monitor patients with acute or chronic kidney dysfunction or failure.
3. Sometimes used as part of a series of tests to evaluate a person's general health status.
What can we learn from the results?
Increased BUN levels (called azotemia) can be a sign of:-
1. Acute or chronic kidney disease. When this is the case there is almost always simultaneous elevation of the creatinine level as well.
2. Kidney damage. (see 1 above)
3. Kidney failure. (see 1 above)
4. Decreased blood flow to the kidneys (due to shock or stress).
5. Dehydration.
6. Urinary tract obstruction such as a kidney stone or an enlarged prostrate.
7. Diabetic nephropathy. (see 1 above)
8. Too much protein in the diet.This sometimes happens when one goes onto a low carbohydrate diet. The idea in these diets is to rather eat a moderate amount of protein and satiate oneself with good fats.
9. Gastrointestinal bleeding such as that caused by an ulcer.
10. Certain medicines can cause elevated BUN readings. (See below)
Decreased BUN levels can be a sign of:-
1. Severe liver disease - inhibits the production of urea.
2. Malnutrition - lack of protein in the diet.
3. Syndrome of inappropriate anti-diuretic hormone secretion (SIADH).
4. Over-hydration
Lower levels are rare and not usually of any concern. Though they may be present in the above diseases they are not used as diagnostic factors. Both decreased and increased BUN concentrations may be seen during a normal pregnancy.
What are 'normal' readings?The range for a BUN does vary depending on factors such as sex and age but around 8–20 milligrams per decilitre (mg/dL) or 3-7 millimoles per litre (mmol/L) is accepted as normal.
BUN is a very sensitive test, and a modest elevation of BUN does not necessarily indicate a need for worry.
Then there are the medicines that could also result in an increased BUN. These include:-
Allopurinol (Alloprin)-- used to lower blood uric acid levels such as found in gout, kidney disease and stones.
Aminoglycosides (Garamycin) - antibiotic used to treat or prevent a skin infection.
Amphotericin (Fungizone) - used to treat oral candidiasis (an oral fungal infection).
Aspirin - used in treating fever, pain, and inflammation. Also to reduce the risk of strokes and heart attacks.
Carbamazepine (Tegretol) - an anti-convulsant used to treat epileptic seizures. Also to treat a painful nerve condition of the face called trigeminal neuralgia.
Cephalosporins - antibiotics used to treat a wide variety of bacterial infection.
Furosemide (Lasix) -a powerful diuretic used to treat edema caused by heart failure, cirrhosis & chronic kidney failure. It is sometimes used with other blood pressure pills to treat high blood pressure.
Guanethidine (Ismelin) - used to treat high blood pressure.
Indomethacin (Indocin) - an anti-inflammatory used for pain, fever and inflammation.
Methotrexate (MTX) - used to treat diseases associated with abnormally rapid cell growth such as certain tumours and psoriasis. Also rheumatoid arthritis.
Methyldopa - used to treat high blood pressure.
Propranolol (Inderal) - used for high blood pressure. Also used to treat angina and to slow and regulate certain types of abnormally rapid heart rates (tachycardias).It has been used to treat migraine headaches and in persons with thyrotoxicosis (high blood levels of thyroid hormone) to slow down rapid heart rate and tremor.
Rifampin (Rifadin) - antibiotic used to prevent and treat tuberculosis.
Spironolactone (Aldacton) - used as a diuretic in cases of congestive heart failure, cirrhosis of the liver, and kidney disease. Also to treat elevated blood pressure in combination with other drugs and in resistant cases of low potassium.
Thiazide diuretics - used to decrease edema and for high blood pressure.
Tetracyclines - a broad-spectrum antibiotic.
Triamterene (Dyrenium) - used to decrease edema and for high blood pressure.
Vancomycin (Vancocin) - an antibiotic used to treat infections.
As can be seen, the situation is very complex and the whole picture needs to be considered in order to reach a conclusion. The BUN test also, like most other tests, only highlights one particular issue and needs to be taken in conjunction with other tests and symptoms to be able to reach a decision about how to interpret the results.
Once again, we get back to the fact that your doctor is the only person who is in the right position to gather together all of the necessary factors. Since many of the potential problems are very serious, it really is essential to deal with elevated BUN levels in conjunction with him or her.
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