Kidney Function Tests Health Article

KEY TERMS

Blood urea nitrogen (BUN)—The nitrogen portion of urea in the bloodstream. Urea is a waste product of protein metabolism in the body.

Creatinine—The metabolized by-product of creatine, an organic compound that assists the body in producing muscle contractions. Creatinine is found in the bloodstream and in muscle tissue. It is removed from the blood by the kidneys and excreted in the urine.

Creatinine clearance rate—The clearance of creatinine from the plasma compared to its appearance in the urine. Since there is no reabsorption of creatinine, this measurement can estimate glomerular filtration rate.

Diuretic—A drug that increases the excretion of salt and water, increasing the output of urine.

Glomerular filtration rate—The rate in millimeters per minute at which plasma is filtered through the glomerular membrane.

Hematuria—The presence of blood in the urine.

Nephrologist—A doctor specializing in kidney disease.

Nephron—The functional unit of the kidney.

Oliguria—The formation of very small amounts of urine.

Osmolality—A measurement of urine concentration that depends on the number of particles dissolved in it. Values are expressed as milliosmols per kilogram (mOsm/kg) of water.

Polyuria—The formation of very large amounts of urine.

Proteinuria—The presence of protein in the urine often caused by damage to the glomerular membrane.

Renal—Pertaining to the kidney

Specific gravity—The ratio of the weight of a body fluid when compared to water.

Urea—A by-product of protein metabolism that is formed in the liver. Because urea contains ammonia, which is toxic to the body, it must be quickly filtered from the blood by the kidneys and excreted in the urine.

Uric acid—A product of purine breakdown that is excreted by the kidney. High levels of uric acid, caused by various diseases, can cause the formation of kidney stones.

Urine—A fluid containing water and dissolved substances excreted by the kidney.

BOOKS

Brenner, Barry M. and Floyd C. Rector Jr., eds. The Kidney, 6th Edition. Philadelphia, PA: W.B. Saunders Company, 1999.

Burtis, Carl A. and Edward R. Ashwood. Tietz Textbook of Clinical Chemistry. Philadelphia, PA: W.B. Saunders Company, 1999.

Kaplan, Lawrence A. and Amadeo J. Pesce. Clinical Chemistry Theory, Analysis and Correlation. St. Louis: Mosby Publishers, 1996.

ORGANIZATIONS

National Kidney Foundation (NKF). 30 East 33rd Street, New York, NY 10016. (800)622-9020. <http://www.kidney.org>.

Jane E. Phillips, PhD