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By Dr. Cynthia Kristensen
The job of your kidneys is to get rid of food and water that becomes waste products, as well as:
Kidney diseases can prevent kidneys from doing their job. Problems such as not removing waste products, allowing blood or protein to leak into the urine or too much potassium in the blood are effects of kidney disease.
Not necessarily. When the kidneys make urine, the urine flows down a tube called the ureter and empties into the bladder. When the bladder becomes full, you feel the urge to pass urine. Some people with severe kidney disease make urine that has a lot of water, but almost no waste products in it. Blood tests for these people show a high level of waste products in the blood, and often other blood tests—such as for potassium—will not be normal.
Some people who urinate frequently are concerned they have kidney disease. However, frequent urination is often a symptom of a bladder—not a kidney—problem. Your doctor should be able to determine the difference by doing blood and urine tests and sometimes x-rays.
Since many kidney diseases do not cause symptoms in the early stages, your doctor can do screening tests to see if you have kidney disease.
The main tests for kidney disease are:
It is important for people who are at risk for developing kidney disease—those with diabetes, high blood pressure or a family member with kidney disease—to be checked regularly.
Diabetes and high blood pressure (hypertension) are the most common causes of kidney disease. Not everyone with diabetes or high blood pressure will develop kidney disease. It’s important for those with these conditions to be checked regularly to find out if their kidneys are affected.
Other causes include:
Most kidney diseases damage the kidneys slowly, over a period of years, hence the term chronic kidney disease. Making the proper diagnosis involves blood and urine tests, a complete physical examination, and sometimes a kidney biopsy.
High blood pressure is never normal. High blood pressure, or hypertension, is known as the “silent killer.” It causes damage to blood vessels in your organs—including brain, heart and kidneys—slowly over a long period of time. Regardless of your age, high blood pressure damages blood vessels, stresses the heart and can damage kidneys. In turn, kidney disease often causes or worsens high blood pressure. It may take two or more different medicines at the same time to control hypertension. It’s important to control blood pressure by getting it to normal levels in order to decrease damage to the kidneys and other organs.
Your doctor can measure the level of creatinine by doing a simple blood test. A normal adult creatinine is about 1.0, regardless of age. We use the level of creatinine to determine the glomerular filtration rate (GFR)—in other words, how well the glomeruli (tiny filters in the kidneys) are filtering out waste products. The 24-hour urine test is called the creatinine clearance and is similar to the GFR.
Kidney function normally declines as we age. The higher the GFR, the better the kidney function. A GFR of 60-100 is generally considered normal (depending on your age and whether you are male or female). Most people do not have symptoms of decreased kidney function until the GFR is 20-30 or less, and some people don’t feel sick until the GFR is as low as 10-15. It’s important for anyone with kidney disease to know their GFR number. Once you know your blood creatinine, you can even calculate your own GFR by using the DaVita.com GFR Calculator.
Symptoms of kidney disease:
When someone has these symptoms, he/she is said to be uremic, or have uremia. For some people, these symptoms may start when the GFR is 20-30, and other people may still feel good until the GFR is under 15. Whether someone has symptoms can also depend on whether he/she has anemia.
Anemia means there are too few red blood cells in the bloodstream. Since red blood cells are needed to deliver oxygen to the tissues, including your heart, muscles, brain and others, your body does not get enough oxygen when you are anemic. Many, if not most, people with poor kidney function have anemia, which makes them more tired. Treating anemia can make people with kidney disease have more energy and generally feel better.
Your doctor will periodically ask if you have any symptoms of uremia. If it’s uremia, your kidney doctor (nephrologist) will determine whether there is anything that can help decrease the kidney damage. You can help by telling your doctor about every medicine you are taking, including over-the-counter (nonprescription) medicines or herbal supplements.
As kidney function lessens, many blood test results become abnormal, and nutrition may worsen. When laboratory tests show that nutrition is deteriorating, it’s often time to start dialysis. Ideally, your doctor will help you become prepared for dialysis or transplantation long before you have uremic symptoms and before your nutrition declines. That way, dialysis or transplantation can be started at the right time so you don’t become severely ill.
To locate a nephrologist in your area, you can use DaVita's Find a Kidney Doctor tool.
Dr. Kristensen is a DaVita nephrologist in Denver, Colorado. She graduated from the University of Minnesota Medical School and did her residency and renal fellowship in Minnesota. Dr. Kristensen spent time working for the University of Chicago hospitals before joining the faculty at the University of Texas Health Science Center at San Antonio.
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