By Dr. Cynthia Kristensen
Your body breaks down food and water and produces waste as a part of daily living. The job of your kidneys is to get rid of those waste products. Each kidney has about a million tiny filters that clean the blood and make urine. Each filter is called a glomerulus. Urine is made up of waste products dissolved in water. Because your body needs to keep certain elements in the blood, such as blood cells and protein, normal glomeruli (plural of glomerulus) do not allow protein or blood to leak from the blood into the urine.
Kidneys also help control many other body functions, including blood pressure, how much blood you make, calcium balance and bone health and the balance of several chemicals in the blood including potassium.
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:
Creatinine is a chemical normally found in the blood. Your kidneys filter the blood and excrete the excess creatinine. If the kidneys cannot get rid of the waste products, the level of creatinine in the blood rises. A person could even have a normal creatinine level in the blood, but have protein or blood in the urine, which may be signs of kidney disease.
High blood pressure can be caused by kidney disease, or can cause kidney disease. Therefore, high blood pressure can be an indication of kidney disease.
Protein in the urine is another sign of kidney disease. Sometimes urine will appear foamy or bubbly when protein is present. A urinalysis will check for protein, blood and white blood cells in the urine (which should not be there). Diabetics should have a yearly urine test for microalbumin, small amounts of protein that don't show up on standard urine protein test.
It is important for people who are at risk for developing kidney disease to be checked regularly. People who are highest risk for kidney disease are those with:
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 is important for those with these conditions to be checked regularly to find out if their kidneys are affected.
There are some inherited forms of kidney disease, such as polycystic kidney disease or Alport syndrome. Some people have a kidney disease that happens as one part of a condition that affects many parts of the body, such as systemic lupus erythematosis, which can also cause arthritis and other problems.
Some kidney diseases occur and we never know why they happen. There are kidney diseases that cause damage rapidly, causing acute (sudden) kidney failure. But 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.
For those who do get kidney disease, kidney failure, or end stage renal disease (ESRD), can often be delayed, and sometimes prevented, by maintaining a healthy lifestyle and getting proper medical care.
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. Doctors used to think the bottom number (the diastolic) was more important than the top number (the systolic), and some people have heard that blood pressure normally increases with age. These are both wrong. We now know that the systolic is as important, if not more important, than the diastolic. 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 high blood pressure. It is 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 (those tiny filters in the kidneys) are filtering out waste products. The GFR is calculated using a mathematical equation, or sometimes by having you collect urine for 24 hours and measuring how much creatinine is in the urine. The 24-hour urine test is called the creatinine clearance and is similar to the GFR.
Kidney function normally declines as we age, so even though the normal blood creatinine is still 1.0 when you are 70-years old, the kidneys filter waste products less efficiently than when you were age 20. 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 is important for anyone with kidney disease to “know your GFR number” and once you know your blood creatinine, you can even calculate your own GFR by using the DaVita.com GFR Calculator.
Swelling in the ankles and legs, or foamy or bloody urine can be signs of kidney disease. These symptoms should be evaluated by your doctor, but they do not necessarily mean that the GFR is low. Many people have no symptoms until the GFR is very low. The waste products that accumulate when the GFR is low are toxins, and can cause:
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, such as: fatigue, poor appetite and itching. Your kidney doctor (nephrologist) will determine if the symptoms are due to uremia and 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. Nutrition is extremely important; when laboratory tests show that nutrition is deteriorating, it is 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.
If you would like to see a doctor who specializes in the care of kidneys, called a nephrologist, you can use DaVita's Find a Kidney Doctor tool to locate a nephrologist in your area.
Dr. Cynthia 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.
She has been on the Medical Review Board for the End Stage Renal Disease Network #15 since the early 1990s and is currently the chairperson for the Network Medical Review Board and the vice-chair of the Board of Directors.
Dr. Kristensen said she went into nephrology because it gave her the opportunity to take care of patients with complicated medical issues and provided the opportunity to provide long-term care and have an ongoing relationship with patients as opposed to brief encounters. Her biggest interest in nephrology is in creating systems that will improve the quality of care for both dialysis patients and patients with chronic kidney disease. She has been practicing with Denver Nephrologists since 1990.
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