Screening For Chronic Kidney Disease
The purpose of screening is early diagnosis and treatment. Screening tests are usually administered to people without current symptoms, but who may be at high risk for certain diseases or conditions. Individuals with the following conditions are at high risk:
- Over 60 years
- Strong family history of chronic kidney disease
- Recurrent ]]>urinary tract infections]]>
- Urinary obstruction
- Medical diseases affecting the kidneys
Early diagnosis and treatment of chronic kidney disease can prevent or delay complications. Since significant kidney disease is usually associated with a decrease in GFR and/or leakage of protein in the urine, the National Kidney Foundation recommends the following screening tests for people at increased risk for chronic kidney disease:
Blood Creatinine Level
Creatinine is a waste product that the kidneys usually remove from the blood. When the kidneys are damaged, the creatinine level rises. A simple blood test can measure the creatine level, which is also used to calculate the glomerular filtration rate.
Estimated Glomerular Filtration Rate
The glomerular filtration rate (GFR) is a measurement of how well the kidneys are processing wastes. Your doctor can calculate the GFR based on your:
- Body size
- Blood creatinine level
The usual formula your doctor uses to estimate GFR is called the Cockcroft-Gault equation:
Estimated GFR (mL per minute) = (140 – age) X body weight in kilogram ÷ 72 X serum creatinine. This product is multipled by 0.85 if estimation is for a female patient.
The GFR determines the stage of chronic renal disease.
|Stage||Glomerular Filtration Rate (GFR)|
|1||Over 90 mL/min (normal)|
|2||60 to 89 mL/min(mild decrease)|
|3||30 to 59 mL/min (moderate decrease)|
|4||15 to 29 mL/min (severe decrease)|
|5||under 15 mL/min (kidney failure)|
Urine Protein Level
During the filtering process, the kidneys usually return protein to the circulation. With chronic kidney disease, the kidneys allow protein to leak into the urine. Different kinds of proteins can leak into the urine. Albumin is a protein that often appears in the urine of people who have chronic kidney disease caused by high blood pressure or diabetes.
The guidelines of the National Kidney Foundation recommend two tests to check the urine protein level:
- Protein-to-creatinine ratio
- Albumin-to-creatinine ratio
To perform these tests, the laboratory compares the amount the protein or albumin to the amount of creatinine in a urine sample.
Depending on your risk factors, your doctor may also order the following screening tests:
Electrolytes, such as sodium and potassium, are minerals needed for the body to work well. Chronic kidney disease causes changes in the electrolytes. A simple blood test can measure the levels of these substances.
Chronic kidney disease causes changes in the concentration of the urine. A simple test can measure the urine concentration.
Chronic kidney disease causes changes in the pH, or acid level, of the urine. A simple test can measure the urine pH.
Are you at risk for chronic kidney disease? National Kidney Foundation website. Available at: http://www.kidney.org/atoz/atozItem.cfm?id=134 . Accessed July 30, 2005.
Hallan SI, Dahl K, Oien CM, et al. Screening strategies for chronic kidney disease in the general population: follow-up of cross sectional health survey. Brit Med J. 2006;333:1047-1053.
Johnson CA, Levey AS, Coresh J, Levin A, Lau J, Eknoyan G. Clinical practice guidelines for chronic kidney disease in adults: Part II. glomerular filtration rate, proteinuria, and other markers. Am Fam Phys. 2004; 70:1091-1097.
K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. National Kidney Foundation website. Available at: http://www.kidney.org/professionals/kdoqu/guidelines_ckd?p9Papproach.htm . Accessed July 30, 2005.
Snively CS, Gutierrez C. Chronic kidney disease: prevention and treatment of common complications. Am Fam Phys. 2004;70:1921-1930.
Last reviewed November 2008 by ]]>Adrienne Carmack, MD]]>
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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