Chronic kidney disease (CKD) is a rapidly growing problem in the United States. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) – a division of the National Institutes of Health (NIH) – reports that between 1990 and 2000, the number of people with kidney failure requiring dialysis or transplantation virtually doubled to 380,000. If this trend continues, the number of people with kidney failure will reach 700,000 by 2010. Treating kidney failure in the United States costs more than $20 billion annually.
What is Chronic Kidney Disease?
Chronic kidney disease (CKD) is the permanent loss of kidney function. Physical injury or a disease which damages the kidneys such as diabetes, polycystic kidney disease or high blood pressure can cause CKD. Kidneys do not remove wastes and extra water from the blood as well as they should when they are damaged.
CKD is considered a silent condition because you can’t often feel or see it. Symptoms are difficult, if not impossible, to notice in the early stages. Because CKD often develops so slowly, many people don't realize they're sick until they are in advanced stages of the disease and must start dialysis immediately to save their life.
How the Kidneys Work
The kidneys are located toward the back of the body on either side of the spine. Each one is about the size of a fist and normally weigh 4 to 6 ounces. While accounting for only 0.5 percent of body weights, the kidney are very busy and important organs. They filter roughly 12 gallons (45 liters) of blood every day, removing approximately a half gallon (1.5 liters) of waste during that same time. Normal functioning kidneys:
- Remove waste products from blood
- Regulate fluid balance in the body
- Regulate electrolytes such as sodium, potassium, calcium, magnesium and phosphorus in the blood
- Regulate blood pressure
- Produce hormones that regulate red blood cell production and calcium metabolism
Why A Transplant Is Necessary
Serious health problems occur when people have less than 25 percent of their kidney function. When kidney function drops below 10 to 15 percent, a person needs renal replacement therapy - dialysis or a kidney transplant - to sustain life.
The determination of when renal replacement therapy is needed is made by testing how well your kidneys are working.
The three main tests of kidney function measure:
- Creatinine levels in the blood
- Glomerular filtration rate (GFR)
- Percent kidney function
Even though the tests are different, they all measure how effectively your kidneys are working. The terms are sometimes used interchangeably. Here is a little more about each one:
Creatinine is a normal byproduct of muscle metabolism that healthy kidneys remove from the blood. Creatinine clearance is tested by taking a 24-hour urine sample and a blood sample and calculating how quickly your kidneys "clear" your blood of creatinine. Creatinine clearance can also be determined by using a formula which provides an approximate value based on blood creatinine level, height, weight and age. Creatinine clearance is reported in milliliters per minute (mL/min). Normally, healthy men have a creatinine clearance between 97-137 mL/min. Healthy women: Between 88-128 mL/min.
Glomerular filtration rate (GFR) is a measure of how fast your blood is filtered through your kidneys. GFR is also reported in milliliters per minute. A GFR greater than 90 mL/min is considered normal.
Percent kidney function is an estimate of remaining kidney function. Because a GFR of 100 milliliters per minute (mL/min) is in the normal range, a rough translation is 100 mL/min is about equal to 100% kidney function. So a creatinine clearance or GFR of 30 mL/min would be called "30% kidney function."
The amount of kidney function is then translated to a “Stage” of chronic kidney disease.