How Are Different Kidney Disease Stages Determined?
The different kidney disease stages classify renal failure according to the level of its severity. There are five (5) distinct categories, ranging from stage 1 to stage 5. These 5 categories help to determine the most effective treatment for patients with kidney disease.
Stage 1 is the mildest degree of kidney failure and at this stage the disease is hardly noticeable.
Stages 2 to 5 are classifications of chronic kidney disease that are progressively more severe. As kidney disease progresses from stage 2 to stage 5, kidney function declines.
Stage 5 is the most severe form of chronic kidney disease and is referred to as end stage renal disease (ESRD).
The time-frame in which kidney disease progresses from stage 1 to stage 5 can be extensive. In some cases it can take up to several months, or years, or sometimes decades for chronic kidney disease to move from sage 1 to stage 5 renal failure.
Chronic kidney disease is the gradual decline of kidney function over an extended period of 3 months or more. When kidney function quickly declines (over a period less than 3 months) it is classified as acute kidney failure.
How Is Kidney Function Measured?
Basically, the degree of kidney failure is determined by the level of kidney function, and kidney function is primarily determined by the glomerular filtration rate (GFR).
GFR is the amount of filtrate that is formed per minute by the kidneys, as they filter the blood to remove waste products. GFR is used to determine the kidney disease stages.
During the process of filtering blood, there is an exchange of fluids and chemicals between the kidneys and blood plasma. Useful chemicals and fluids are returned to the blood plasma but waste products are converted to urine, which is subsequently expelled from the body.
The Glomerulus is the primary filtering unit of microscopic structures in the kidneys known as nephrons. As the Glomerulus filters the blood it forms a fluid called Glomerular filtrate. This fluid is similar to blood plasma except that it has almost no protein.
On average, healthy female kidneys produce about 105 mL/min of Glomerular filtrate, while healthy male kidneys produce about 125 mL/min.
Kidney Disease Stages Defined
The diagram on the right provides an overview of the different kidney disease stages. Source: National Kidney Foundation.
Stage 1:
- Stage 1 is the least severe of the five kidney disease stages. GFR is 90% or above and there may be no noticeable signs or symptoms of kidney failure. In many cases, stage 1 chronic kidney disease is only discovered during routine medical examinations.
Medication may not be necessary but patients with stage 1 kidney disease may be advised to take steps to modify their lifestyle and diet, in order to preserve kidney function.
Stage 2:
- When GFR falls within the range of 60 to 89 percent, the patient is diagnosed with stage 2 chronic kidney disease. This stage is considered mild.
Patients may require treatment for underlying conditions, such as diabetes and hypertension. These underlying conditions may be early indicators of stage 2 or other more severe stages of renal failure. Patients who develop hypertension or diabetes should have their kidney function checked regularly.
Stage 3:
- Stage 3 has a GFR range of 30-59%. At this stage, kidney failure is classified as moderate.
The primary treatment for kidney disease stages that are classified as mild or moderate (stages 1 to 3) mainly focuses on diet, exercise and medication for underlying conditions (such as hypertension and diabetes).
The next two stages of kidney disease are classified as severe. Treatment for severe chronic kidney disease requires more than just diet, exercise and medication for underlying conditions.
Stage 4:
- Stage 4 chronic kidney disease is classified as severe. At this stage, GFR falls within the range of 15-29%. Kidney function declines significantly and the kidneys are no longer able to adequately filter the blood and maintain homeostasis (ho-me-oh-stay-sis).
In addition to diet, exercise and medication for underlying conditions, treatment of stage 4 chronic kidney disease includes dialysis.
Stage 5:
- Stage 5 is the most severe stage of kidney failure... GFR is less than 15%. Stage 5 kidney failure is also known as end stage renal disease (ESRD). The kidneys virtually stop working, so patients with stage 5 renal failure must receive regular dialysis.
The long-term treatment for ESRD is a kidney transplant.
The early stages of kidney disease can be detected by routine medical examinations. It is, therefore, advisable to have regular medical check-ups (at least once a year).
Early detection of chronic kidney disease provides the best opportunity for effective treatment, which can help to prevent or delay adverse outcomes associated with chronic kidney disease. The first two kidney disease stages (stages 1 and 2) offer the greatest possibilities for effective treatments.