Understanding Kidney Disease
It is estimated that kidney disease affects 31 million people in the United States alone, and globally 1 in 10 people have some form of kidney disease. Also called renal disease, kidney disease is the general term for damage that reduces function of the kidney. Chronic kidney disease (CKD) occurs when kidneys are no longer able to clean toxins and waste product from the blood and perform their functions to full capacity. This can happen all of a sudden or over time.1
Every day, our two kidneys filter about 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine, composed of wastes and extra fluid.2 Healthy kidneys help regulate blood pressure, remove waste and water, signal your body to make red blood cells, and help regulate growth in children.
In addition to the different phases of kidney disease (listed below), there are different types of kidney disease, with different causes and requiring different treatments. NKI and this website provide detailed information about the diseases that cause Nephrotic Syndrome (NS) and Focal Segmental Glomerulosclerosis (FSGS).
Five Stages of Kidney Disease
The National Kidney Foundation (NKF) created a guideline to help doctors identify each level of kidney disease. The NKF divided kidney disease into five stages. Identifying the stage of kidney disease a person is in helps health care practitioners provide the best care, since each stage requires different treatment.
To understand each stage, we must first understand how kidney function is measured. The universally accepted measure of kidney function is the Glomerular Filtration Rate (GFR). Kidney function is measured by how effectively your kidneys clean your blood. The main way of estimating GFR is a blood test to determine the level of Creatinine in the blood, or serum creatinine. As kidney function declines, the levels of creatinine increase.
An equation is used to determine GFR. In addition to serum creatinine, factors such as age, race, and gender are included in the equation. Additional factors that may be included are weight, blood urea nitrogen (BUN), and serum albumin.
The five stages of kidney disease, and the GFR for each stage, is shown below:
- Stage 1 with normal or high GFR (GFR > 90 mL/min)
- Stage 2 Mild CKD (GFR = 60-89 mL/min)
- Stage 3A Moderate CKD (GFR = 45-59 mL/min)
- Stage 3B Moderate CKD (GFR = 30-44 mL/min
- Stage 4 Severe CKD (GFR = 15-29 mL/min)
- Stage 5 End Stage CKD (GFR <15 mL/min)
You can find more information on glomerular kidney diseases, specifically the condition called Nephrotic Syndrome (NS), Focal Segmental Glomerulosclerosis (FSGS), and Minimal Change Disease (MCD), using the navigation links on the right sidebar of this page.
Additional information on each stage of kidney disease can be found here.