How to read a kidney function lab report
Oct 26, 2023
Source: Cainiu Health
Dr. Yang Ziqi
Introduction
Kidney function can be assessed using indicators such as creatinine, blood urea nitrogen (BUN), cystatin C, and β2-microglobulin. Creatinine is a metabolic byproduct of muscle activity and is primarily excreted by the kidneys. Because creatinine levels are typically stable, it is commonly used as a marker to evaluate glomerular filtration rate and overall kidney function. These indicators are usually interpreted alongside other clinical findings and imaging studies to provide a comprehensive assessment of kidney function and health.
In general, kidney function can be assessed from blood tests by examining indicators such as creatinine, blood urea nitrogen (BUN), cystatin C, and β2-microglobulin. The specific analysis is as follows:
1. Creatinine
Creatinine is a metabolic byproduct of muscle activity and is primarily excreted by the kidneys. Because creatinine levels are usually stable, it is commonly used as an indicator to evaluate glomerular filtration rate (GFR) and overall kidney function. The normal reference ranges are 54–106 μmol/L for adult males, 44–97 μmol/L for adult females, and 24.9–69.7 μmol/L for children. Elevated creatinine levels may indicate reduced kidney function and often suggest kidney damage, which could be related to acute or chronic kidney disease.
2. Blood Urea Nitrogen (BUN)
BUN measures the concentration of urea in the blood, with a normal range of 2.86–7.14 mmol/L. Urea is a byproduct of protein metabolism and can also be used to assess kidney function. Elevated BUN levels may indicate impaired kidney function, although they can also be influenced by other factors such as dehydration or a high-protein diet.
3. Cystatin C
Cystatin C is a protein that is filtered by the renal tubules and almost completely reabsorbed. Therefore, cystatin C levels can be used to estimate glomerular filtration rate, with a reference range of 0.51–1.09 mg/L. Increased cystatin C levels may indicate reduced kidney function and are associated with a decreased GFR.
4. β2-Microglobulin
β2-Microglobulin is a small protein that may leak into the urine when renal tubules are damaged. The normal reference range is 1.0–2.6 μg/L. Elevated levels typically indicate impaired tubular function and may be associated with tubular diseases or other kidney problems.
These markers are typically used alongside other clinical evaluations and imaging studies to comprehensively assess kidney function and health. It is recommended to consult a physician for proper interpretation.
