The National Institute of Diabetes and Digestive and Kidney Diseases reports that an estimated 23 million American adults have chronic kidney disease, also known as chronic kidney failure. The definition of chronic kidney disease is evidence of a physical or functional kidney abnormality lasting three or more months. Guidelines to categorize chronic kidney disease into five stages based on disease severity were established by the National Kidney Foundation in 2002. The stages of chronic kidney disease are numbered 1 through 5 based on increasing disease severity.
Stage 1
The primary factor in distinguishing the various stages of chronic kidney disease is a measurement called the glomerular filtration rate, or GFR. GFR estimates the quantity of blood filtered and processed by the kidneys per minute. People with stage 1 chronic kidney disease have a GFR greater than or equal to 90 ml per minute per 1.73 m squared. For simplicity, GFR is usually discussed in terms of milliliters per minute. Typically, there are no kidney-related symptoms with stage 1 disease despite laboratory evidence of kidney damage such as protein in the urine. Medical care focuses on controlling the underlying cause of the kidney damage and preventing disease progression.
Stage 2
People with stage 2 chronic kidney disease have a GFR of 60 to 89 ml per minute. Despite a decreasing GFR, most people with stage 2 disease do not have kidney-related symptoms. As with stage 1 disease, medical care focuses on the underlying cause of the disease and preventing progression.
Stage 3
Stage 3 chronic kidney disease is defined by a GFR of 30 to 59 ml per minute, which represents a moderate decrease in kidney function. Most people do not have kidney-related symptoms until the GFR approaches the level of stage 4 chronic kidney disease. Medical efforts focus on underlying disease control and preventing its progression.
Stage 4
With stage 4 chronic kidney disease, the GFR is 15 to 29 ml per minute, which represents a severe decline in kidney function. Kidney-related symptoms are the norm with this stage of kidney failure. Urination may be increased or decreased. Fatigue, loss of appetite, nausea and vomiting are common. Swelling or edema, especially in the feet and lower legs, is also common. Widespread itching often occurs due to a buildup of chemicals in the skin that cannot be excreted by the kidneys. Medical care focuses on correcting metabolic disturbances, controlling symptoms and slowing disease progression.
Stage 5
With stage 5 chronic kidney disease, the GFR is less than 15 ml per minute. This represents kidney failure, also known as end-stage renal disease, or ESRD. Regular dialysis is necessary to remove waste products from the blood that would normally be excreted by the kidneys. People with ESRD are chronically ill with all the symptoms of stage 4 disease typically present in a more severe form. Most people with stage 5 chronic kidney disease are placed on the kidney transplant list, if they so desire. The 2009 annual report from the U.S. Renal Data System states that more than 527,000 Americans were living with ESRD in 2007.
References
- National Institute of Diabetes and Digestive and Kidney Diseases: Kidney and Urologic Diseases Statistics for the United States
- American Family Physician: Clinical Practice Guidelines for Chronic Kidney Disease in Adults
- National Kidney Foundation: Definition and Classification of Stages of Chronic Kidney Disease
- National Kidney Foundation: What is Glomerular Filtration Rate (GFR)?
- National Institute of Diabetes and Digestive and Kidney Diseases: The Kidneys and How They Work
