Kidney Function Tests
Kidney function tests are tests performed to evaluate kidney function and identify any abnormalities. Some of the commonly conducted laboratory tests are
- BUN test – blood, urea, and nitrogen
- Creatinine – blood
- Creatinine clearance
- Creatinine urine
Blood urea nitrogen (BUN): The BUN test measures the nitrogen content in blood urea. Urea is a waste product released from degradation of protein, which is filtered in the blood and excreted in urine by kidneys. The normal values of nitrogen in blood urea ranges from 7 to 20mg/dL. Elevated levels suggest impaired kidney function such as acute or chronic kidney disease and decreased blood flow to kidneys as in congestive heart failure and shock. Decreased concentration of BUN is not common and may occur in cases of malnutrition and severe kidney disease.
Blood Creatinine: This test measures the amount of creatinine in blood which signifies the filtering capability of the kidneys. Creatinine is a by-product of creatine produced when muscles are put to use. Creatinine is filtered from blood and excreted in urine by the kidneys. Normal value of creatinine is 0.8 – 1.4mg/dL. Females have low creatinine than males because of the muscle mass. If the level of creatinine is more than the normal value it indicates kidney conditions such as glomerulonephritis, pyelonephritis, acute tubular necrosis, kidney stones, prostate disease, and complications of diabetes. Creatinine levels may be decreased slightly in pregnancy.
Creatinine clearance: This test determines the kidney functioning and suggests kidney dysfunction or decreased blood flow to kidneys as in congestive heart failure. Creatinine is the waste product released when the muscle is put to work. Creatinine clearance is also done to estimate the glomerular filtration rate (GFR). The normal value in males is 97 to 137 mL/min and in females is 88 to 128mL/min. A high GFR may indicate kidney failure.
Urine creatinine: This test measures the amount of creatinine in urine. Creatinine is filtered by the kidneys and excreted in urine. The normal value of creatinine in urine is 500 to 2000 mg/day which may vary with age. Any derangement in the values signifies the impaired kidney function.