The kidneys act as one of the body's main waste processing plants, filtering about 200 quarts of blood each day, according to the National Institute of Diabetes and Digestive and Kidney Disorders. A tumor in the kidney limits its ability to eliminate waste products from the blood. Levels of BUN, which stands for blood urea nitrogen, rise as waste products accumulate in your blood. Many kidney disorders cause a rise in BUN; you don't necessarily have kidney cancer if your BUN rises. An elevated BUN does indicate abnormal kidney functioning and does require follow-up with your medical provider.
Definitions
Urea nitrogen is a waste product formed when your liver--the other--toxin processing center in the body--breaks down ammonia. Ammonia is a byproduct of protein breakdown. The nitrogen in the ammonia combines with carbon, hydrogen and oxygen to form urea. The kidneys normally filter urea out of the blood so it can be eliminated from the body in the urine. Since most people have two working kidneys, even if one is damaged, the other one can work to keep your BUN low. A normal BUN level is 8 to 24 mg/dL for men and 6 to 21 mg/dL for women, according to MayoClinic.com. A higher BUN indicates that less of the kidney is functioning.
Effects
If a tumor is blocking part of the filtering system within the kidney, the amount of urea that can be filtered out is decreased and the BUN rises. However, increased protein intake, fever, urinary tract infection or dehydration as well as other kidney disorders can also cause a temporary rise in the BUN. Many drugs can also affect your BUN.
Diagnosis
An elevated BUN indicates a kidney problem of some type. Further testing is required to determine the cause. A renal ultrasound, which is another name for a kidney ultrasound; computed tomography, also called a CT scan; or magnetic resonance scan, also called an MRI, can all evaluate the kidney for possible tumors. Around 33,000 people each year are diagnosed with renal cell carcinoma, the most common type of kidney cancer, according to the American Cancer Society. The BUN level does not indicate the type of tumor.
Prevention and Treatment
Smokers are twice as likely to develop kidney cancer as nonsmokers. Not smoking is the single best way to reduce your chance of developing kidney cancer, University of Miami Leonard M. Miller School of Medicine explains. Early diagnosis and treatment gives the best chance of survival in kidney cancer. An abnormal BUN is one of the first signs of kidney dysfunction and should never be ignored. In most cases, only one kidney is affected in kidney cancer, and only a single tumor is found. Treatments include removal of the kidney or removal or destructions of just the tumor, if possible. The five-year survival rate for kidney cancer overall is 40 to 45 percent, according to the Leonard M. Miller School of Medicine.
References
- University of Miami Leonard M. Miller School of Medicine: Kidney Cancer; 2007
- Cleveland Clinic Foundation: Nephrotoxicity (Renal Toxicity); 2005
- MayoClinic.com: Blood Urea Nitrogen Test; December 2010
- National Institute of Diabetes and Digestive and Kidney Disorders; The Kidneys and How They Work; February 2009
