Interviewer: Dr. Narva explains that kidney disease is diagnosed with two tests and followed with the same two tests -- a blood and urine test.
Dr. Narva: The blood test measures a substance called creatinine which is a waste product from muscle. That waste product is removed by the kidneys and comes out in the urine. If your kidneys are damaged the level of creatinine goes up and we can estimate from that how well your kidneys are filtering. The result is something called the "estimated glomerular filtration rate," which is a long word but it's something that everyone needs to know. If you ask your doctor what's your GFR -- your glomerular filtration rate -- he or she should be able to tell you. It's a number and even though it takes a little explaining to understand what it is, it's a number that you can remember, it's a number that you can compare to your last visit and it can really help you know how well your kidneys are working. The other test, the measure of protein in the urine, is a sign that the kidney filter is damaged in some way. Protein is what your body is made of -- your muscles, your skin and your hair. You get protein from eating foods like meat and fish and chicken and those foods are absorbed into your blood and circulated in your body in very small particles. Even though those protein particles are very small they're too big to pass through a normal kidney filter, so if we see protein in the urine it tells us that the kidney filter is damaged in some way. That's very important because even small amounts of protein in the urine signal to us that you're at risk not only of having more serious kidney injury but also it's a very good indicator of risk for heart disease.