Kidney Disease
- Facts about Chronic Kidney Disease (CKD)
- What are the kidneys and why are they important?
- How do kidneys help maintain health?
- What is chronic kidney disease?
- Are there different stages of kidney disease?
- How does a person know if they have kidney disease?
- What are the tests for chronic kidney disease?
- What are some other common laboratory tests?
- What is glomerular filtration rate (GFR)?
- What does GFR indicate?
- Should serum creatinine alone be used to estimate kidney function?
- Who is at risk for getting chronic kidney disease?
- What should be done if a person is at increased risk for kidney disease?
- Can kidney disease be treated?
- Does kidney disease affect the body in other ways?
- What is the impact of kidney disease on health care costs?
- Key points to remember
- A Quick Guide to Blood Test Values [pdf]
- Glossary [pdf]
Facts about Chronic Kidney Disease (CKD)
- More than 26 million American adults and thousands of American children have
chronic kidney disease. Millions more are at increased risk for developing chronic
kidney disease. - More than 50 million people worldwide have chronic kidney disease, and more than one million of them are receiving kidney replacement therapy.
- Early detection may help slow the progression of kidney disease and help avoid kidney failure.
- Most people with chronic kidney disease do not die of kidney failure - they die of heart disease. In fact, heart disease causes 40-50% of all deaths in patients with chronic kidney disease. Most of these deaths occur before dialysis or transplant is necessary.
- Persistent protein in the urine (two positive tests over approximately 3 months) is an early sign of chronic kidney disease.
- The best way to measure kidney function is to calculate estimated glomerular filtration rate (eGFR).
- An eGFR less than 60 for 3 months or more is considered to be CKD.
- According to the Centers of Disease Control and Prevention (CDC), the burden of chronic kidney disease, in terms of human suffering and economic costs, is exploding as we move through the early years of the 21st century, making it a major public health issue." [Source: Schoolwerth AC, Engelgau MM, Hostetter TH, Rufo KH, Chianchiano D, McClellan WM, et al. Chronic kidney disease: a public health problem that needs a public health action plan. 2006 Apr 2007. www.cdc.gov/pcd/issues/2006/apr/05_0105.htm.]
What are the kidneys and why are they important?
The human body has two kidneys. Each kidney is about the size of a fist. They are located near the middle of the back, just below the rib cage. Each kidney has about 1.5 million filters, called nephrons. Nephrons remove waste and extra fluid from blood in the form of urine. The urine flows through two tubes, called ureters, to the bladder. The urine is stored there until it is passed during urination. The waste comes from the breakdown of food eaten and medicine taken, plus normal muscle and organ activity.
How do kidneys help maintain health?
Kidneys are important because they keep the rest of the body's systems in balance by:
- Removing waste products from the body
- Regulating blood levels of chemicals such as potassium, sodium, calcium and magnesium
- Balancing the body's fluids
- Helping to keep blood pressure under control
- Keeping bones healthy
- Helping make red blood cells
What is chronic kidney disease?
Chronic kidney disease (CKD) means the kidneys have become damaged. Kidneys can get damaged from a physical injury or a disease like diabetes or high blood pressure. Once the kidneys are damaged, they cannot filter blood or do their other jobs as well as they should.
In the early stages of the disease, most people do not have any symptoms. But as kidney disease gets worse, wastes and fluid may build up in the blood and cause symptoms such as swelling, increased blood pressure, nausea and vomiting, and poor appetite.
Chronic kidney disease is a serious, life-threatening disease that requires treatment. But with early detection and treatment, it may be possible to prevent chronic kidney disease and its complications from getting worse. Without treatment, chronic kidney disease can progress to kidney failure. A person who has kidney failure will need regular dialysis treatments or a kidney transplant to stay alive.
Lab tests are critical in detecting CKD. They give physicians information about the severity of each patient's condition and guidance in selecting the best treatments.
Are there different stages of kidney disease?
There are five stages of chronic kidney disease (shown in the table below). A doctor determines which stage of kidney disease a person has based on the presence of kidney damage and glomerular filtration rate (GFR), which is a measure of kidney function.
| Stages of Kidney Disease | ||
| Stage | Description | Glomerular Filtration Rate (GFR) |
| 1 | Kidney damage (e.g. protein in the urine) with normal GFR | 90 or above |
| 2 | Kidney damage with mild decrease in GFR | 60 to 89 |
| 3 | Moderate decrease in GFR | 30 to 59 |
| 4 | Severe reduction in GFR | 15 to 29 |
| 5 | Kidney failure | Less than 15 |
| * Your GFR number tells your doctor how much kidney function you have. As chronic kidney disease progresses, your GFR number decreases. Reprinted with permission from the National kidney Foundation |
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How does a person know if they have kidney disease?
Chronic kidney disease can be a silent disease that progresses slowly over many years. In fact, in the early stages of the disease, most people do not have any symptoms and may not know they have the disease. The best and most reliable way for someone to find out if they have kidney disease is to get tested for it.
What are the tests for chronic kidney disease?
There are three simple tests to screen for chronic kidney disease:
- Blood test for creatinine to estimate GFR
A doctor tests the blood for a waste product called creatinine. Creatinine comes from muscle tissue. When the kidneys are damaged, they have trouble removing creatinine from blood. The creatinine result is used in a math formula to find out the person's GFR number.
- Regular blood pressure checks
Having high blood pressure puts people at risk for chronic kidney disease. High blood pressure can also be caused by chronic kidney disease. In other words, it is both a risk factor for kidney disease as well as a complication of kidney disease.
Regular blood pressure checks help doctors find and treat high blood pressure. This helps lessen the risk for getting kidney damage and for kidney damage getting worse.
- Urinalysis to detect proteinuria
The human body needs protein. But it should be in the blood, not in the urine. Having protein in the urine (called proteinuria) may mean that a person has kidney damage. Proteinuria can be a sign of early kidney disease. Albumin is a type of protein. The term microalbuminuria refers to small but abnormal amounts of albumin, and may be an early sign of CKD in people with diabetes.
Evaluation of proteinuria in patients not known to have kidney disease.
National Kidney Foundation, KDOQI Clinical Practice Guidelines for Chronic Kideny Disease:
Evaulation, Classification and Stratification,
Reprinted with permission from the National Kidney Foundation
| Definitions of Proteinuria and Albuminuria | ||||
| Urine Collection Method | Normal | Micro-albuminuria | Albuminuria or Clinical Proteinuria | |
| Total Protein | 24-Hour Excretion (varies with method) | <300 mg/day | NA | >300 mg/day |
| Spot Urine Dipstick | <30 mg/dL | NA | >30 mg/dL | |
| Spot Urine Protein-to-Creatinine Ratio (varies with method) | <200 mg/g | NA | >200 mg/g | |
| Albumin | 24-Hour Excretion (varies with method) | <30 mg/day | 30-300 mg/day | >300 mg/day |
| Spot Urine Albumin-Specific Dipstick | <3 mg/dL | >3 mg/dL | NA | |
| Spot Urine Albumin-to-Creatinine Ratio (varies by gendera) | <17 mg/g (men) <25 mg/g (women) |
17-250 mg/g (men) 25-355 mg/g (women) |
>250 mg/g (men) >355 mg/g (women) |
|
| a. Gender-specific cut-off values are from a single study. Use of the same cut-off value for men and women leads to higher prevalence for women than men. Current recommendations from the American Diabetes Association define cut-off values for spot urine alubmin-to-creatinine ration for microalbuminuria and albuminuria as 30 and 300 mg/g, respectively, without regard to gender. National Kidney Foundation, KDOQI Clinical Practice Guidelines for Chronic Kideny Disease: Evaulation, Classification and Stratification, Am J Kidney Dis 39, 2002 (suppl 1) Reprinted with permission from the National Kidney Foundation |
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What are some other common laboratory tests?
- Albumin
- Albumin is a type of protein. Albumin tests help in the evaluation of liver
disease, kidney disease, and other conditions. Albumin in the urine can be a sign of
early kidney disease. Decreased serum albumin occurs with malnutrition, low protein diets, or increased urinary loses. - Blood Urea Nitrogen (BUN)
- Urea nitrogen is a normal waste product in the blood
that comes from dietary protein and body stores of protein. Healthy kidneys maintain
normal BUN, but when kidney function is impaired, BUN levels go up. In other words, the BUN level increases as kidney function decreases. - BUN:Creatinine
- This is a ratio of BUN to plasma creatinine. It is used in the differential diagnosis of acute kidney injury.
- Calcium
- This test helps screen for, diagnose, and monitor a range of conditions relating to the bones, heart, nerves, and kidneys. Blood calcium levels do not directly tell how much calcium is in the bones, but rather, how much calcium is circulating in the blood. People with chronic kidney disease often develop problems with their bones due to abnormal blood calcium levels. In people with CKD, calcium should be evaluated along with phosphorus and PTH levels.
- Carbon dioxide
- This test is used to detect acid-base disturbances which are seen in patients with severe chronic kidney disease or kidney failure.
- Chloride
- This test helps evaluate electrolyte or acid-base balance. Some people with kidney disease have an abnormal blood chloride level.
- Creatinine
- Creatinine comes from muscle tissue. When the kidneys are damaged, less creatinine is filtered from blood and excreted in the urine. The creatinine result is used in a math formula to find out the person's GFR number. Estimating GFR is the best measure of kidney function. Serum creatinine alone should not be used to measure kidney function.
- Glucose
- This test determines if blood glucose level (BGL) is within normal range. BGL is useful for screening, diagnosing, and monitoring of hyperglycemia, hypoglycemia, diabetes, and pre-diabetes. Diabetes is a leading cause of chronic kidney disease.
- Phosphorus
- Blood phosphorus level is usually controlled by the kidneys which excrete phosphorus in the urine. A high phosphorus level can lead to weak bones in people with chronic kidney disease for whom mineral and bone disorders are a complication. This test is used to evaluate the level of phosphorus in blood, and toaid in the diagnosis of conditions known to cause abnormally high (as in as kidney disease) or low levels. In people with CKD, blood phosphorus should be evaluated along with calcium and PTH levels.
- Potassium
- Potassium is a mineral that helps the heart and muscles work properly. Kidneys are essential to keeping blood potassium levels in balance. A potassium level that is too high (hyperkalemia) or too low (hypokalemia) can be harmful and needs to be treated to bring the level to normal range. Patients with more advanced chronic kidney disease can have abnormal potassium levels.
- Sodium
- This test is used to monitor chronic or acute hypernatremia (high blood sodium) or hyponatremia (low blood sodium), and as part of an evaluation of electrolyte balance and kidney function. Patients with high blood pressure and chronic kidney disease may be asked to limit their salt intake.
For more detailed information on blood test values, see "A Quick Guide to Blood Test Values" [pdf]
What is glomerular filtration rate (GFR)?
Estimating GFR is the best way to evaluate how well a person's kidneys are working. It also helps a doctor find out a person's stage of chronic kidney disease. A doctor or medical laboratory can calculate a person's GFR number from the person's blood creatinine level, age, race and gender.
What does GFR indicate?
GFR indicates the level of kidney function.
- In most healthy people, the normal GFR is 90 or higher.
- A result between 60 and 89 without kidney damage may be normal in some people (elderly, infants)
- A result between 60 and 89 for three months or more along with kidney damage (such as persistent protein in the urine) means the person has early kidney disease.
- When GFR is below 60 for three months or more, CKD is present.
Should serum creatinine alone be used to estimate kidney function?
No. Serum creatinine alone is not the best way to detect early stage kidney disease. This is because a rise in blood creatinine levels is observed only after significant loss of functioning nephrons (which are the filters of the kidneys). A better way to measure kidney function is to estimate GFR. GFR can be estimated with equations that use serum creatinine levels and some or all of the following variables: gender, age, weight, and race.
Who is at risk for getting chronic kidney disease?
Anyone can get chronic kidney disease at any age. However, some people are more likely than others to develop kidney disease. The chances of getting kidney disease are greater if a person:
- Is African American, Hispanic American, Asian, Pacific Islander or American Indian
- Has diabetes, high blood pressure, or hepatitis C
- Has a family member with kidney disease
- Is 65 or older
- Has used medications over the course of many years that damage the kidneys
Each risk factor listed above increases a person's chance of getting kidney disease. The more risk factors a person has, the greater the risk.
What should be done if a person is at increased risk for kidney disease?
Individuals who have risk factors for developing kidney disease should:
- Be tested regularly for kidney disease
This should include testing for markers of kidney damage (such as proteinuria), estimating GFR, and checking blood pressure .
- Control diabetes
Diabetes is a leading cause of chronic kidney disease. In fact, about a third of people with diabetes may get chronic kidney disease. Strict control of blood sugar levels has
been proven to lower the risk of developing kidney disease.
- Control high blood pressure
High blood pressure is another leading cause of kidney disease. Lowering blood pressure and keeping it under control can help reduce that risk. Steps to reduce blood
pressure may include:- Taking antihypertensive medication, if necessary
- Avoiding tobacco. Smoking raises blood pressure.
- Eating less salt. Keeping salt intake low reduces blood pressure.
- Avoiding alcohol. Alcohol increases the chance of developing high blood
pressure. It can also affect medicines and make it harder to control blood
pressure.
- Lose excess weight to help control blood pressure and diabetes.
- Follow a program of regular physical exercise approved by a doctor.
Regular exercise helps control blood sugar and blood pressure - two major risk factors for developing kidney disease. Even mild exercise like walking or strolling
can be helpful.
Can kidney disease be treated?
The earlier kidney disease is found, the better. If it is found and treated early, it may be possible to slow progression to the more advanced stages of kidney disease and reduce CKD complications. That is why it is so important for people with risk factors to be tested regularly. The success of treatment depends on a number of things:
- The person's stage of chronic kidney disease when they start treatment. The earlier it's treated, the better.
- How carefully a person follows the treatment plan. People with kidney disease should learn all they can about the disease, and follow treatment carefully.
Does kidney disease affect the body in other ways?
Chronic kidney disease may cause problems throughout a person's entire body. Some of the most common complications are:
- Heart and blood vessel problems
- Anemia (low red blood cell count)
- Mineral and bone problems
- High blood pressure
- Poor nutritional health
As part of the treatment plan, a doctor will work closely with the patient to help prevent or treat these problems.
What is the impact of kidney disease on health care costs?
The impact of CKD to health care cost is high.
- CKD affects an estimated 11% of the US population, and those affected are at increased risk of cardiovascular disease, kidney failure, and premature death.
- The disease is especially costly because it is often more than one disease-occurring frequently with heart disease, diabetes, high blood pressure, anemia, bone and
mineral disease, and other complications. - Kidney disease accounts for 16.5% of Medicare expenditures, nearly double that of 10 years ago.
- Costs for Medicare patients with CKD exceeded $49 billion in 2006 - nearly 5 times greater than costs in 1993. Expenditures for patients with CKD now account for nearly one-quarter (24.5%) of Medicare spending.
- It is estimated that by 2030, more than 2 million people in the United States will have
kidney failure, the form of CKD in which life can only be sustained by dialysis or
transplantation.
Key points to remember
Most people with CKD are unaware that they have the disease. In fact, nearly half of people with an advanced form of kidney disease do not know they have weak or failing kidneys, according to recent research published in the American Journal of Kidney Diseases, the official journal of the National Kidney Foundation.
- Early detection and treatment may help slow the progression of kidney disease and help avoid kidney failure.
- CKD is not being detected early enough to initiate treatment and reduce death and disability.
- Kidney disease is listed as the ninth leading cause of death in the United States by the Centers for Disease Control and Prevention (CDC).
- Heart disease is the major cause of death for all people with CKD.
- Hypertension causes CKD and CKD causes hypertension.
- Diabetes is a leading cause of chronic kidney disease in developing countries. Today it accounts for 45% of kidney failure - up from 18% in 1980.
- Persistent protein in the urine (two positive tests over approximately 3 months) is an early sign of chronic kidney disease.
- People with diabetes, hypertension and family history of kidney disease are at high risk for developing CKD.
- African Americans, Hispanics, Pacific Islanders, Native Americans and Seniors are at increased risk.
- Age alone is a key predictor of CKD. In fact, 11% percent of people in the United
States aged 65 years or older (without diabetes or hypertension) have moderately to
severely decreased kidney function. - Considering that kidney failure costs Medicare more than $20 billion every year-
with rapid growth ahead-early detection means dollars saved (along with all those
kidneys). - The best way to measure kidney function is to calculate estimated glomerular filtration rate (eGFR).
For more information
For more information, contact:
The National Kidney Foundation (NKF)
30 East 33rd Street
New York, NY 10016
800.622.9010
www.kidney.org
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