Wednesday, April 13, 2005

Check Your Filter

The kidneys are much busier organs than most people realize. In addition to filtering toxins from the blood, the kidneys balance fluid content in the body... produce the enzyme renin that helps control blood pressure... produce the hormone erythropoietin to help make red blood cells... activate vitamin D to maintain healthy bones... and adjust levels of minerals and other chemicals to keep the body working properly. Now a recent large study shows a direct link between chronic kidney disease (CKD) and an increased risk of developing cardiac disease. This is especially disturbing because anywhere from 10 million to 20 million Americans have kidney disease, and many of them are completely unaware of it.
The lead author of the study, Alan S. Go, MD, is a research scientist and senior physician at Kaiser Permanente of Northern California. I spoke with Dr. Go about his study, which was funded by the National Institute of Diabetes and Digestive and Kidney Diseases. The research team followed more than 1.1 million adults, average age 52 years, for nearly three years. They discovered that when kidney function began to falter, even among those whose kidney disease was not extreme, there was a dramatic increase in hospitalization and risk of death by heart disease and stroke. Dr. Go says that the message from this study is twofold. First, people with even one risk factor for kidney disease -- high blood pressure (even if successfully medicated), diabetes, family history of CKD or being elderly -- require regular testing for kidney disease. Second, if kidney disease is present -- even in its earliest stages -- address it aggressively through lifestyle adjustments, including a heart-healthy diet, regular exercise and not smoking. This will help decrease related disease risks, but if lifestyle changes don't control blood pressure or blood sugar levels, patients should talk to their doctors about taking medication that will.
To test for kidney disease, scientists have developed a rating called glomerular filtration rate (GFR) as an extension of the standard creatinine blood test. The creatinine blood test measures the amount of a muscle protein waste byproduct that the kidneys filter out. Too much in the blood shows that the kidneys are not removing it properly. GFR is based on a simple equation that factors race, gender and age into the serum creatinine level. The GFR is the real indicator of kidney health at this time, says Dr. Go. Anyone with a GFR of 60 or less is considered at risk for chronic kidney disease and requires further testing, including another creatinine test, a urine protein test and testing for related diseases, including cardiovascular disease. While the GFR tells about kidney function, it says nothing about the cause of renal impairment. (Note: The GFR is structured to reflect accuracy in readings 60 and under. Results over 60 actually may be higher than given, says Dr. Go.) Doctors and labs are beginning to incorporate GFR routinely, but be sure to request it any time you have a creatinine test.

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