There are five stages of chronic kidney disease, each one associated with a glomerular filtration rate that progressively decreases from stage 1 to stage 5. The glomerular filtration rate, or GFR, refers to the rate at which the glomerulus filters waste, ions, and water in the blood. A normal GFR is considered to be greater than 90 millilitres per minute. This number is calculated based on creatinine clearance level, gender, age, race, and weight. As the glomerular filtration rate decreases, issues with waste, electrolyte imbalances, and fluid overload will arise.
Stage 1 is characterized by kidney damage with normal renal function, and is associated with a normal or high GFR, greater than 90 millilitres per minute, as well as proteinuria for 3 months or more. Proteinuria, in short, refers to the presence of greater than normal amounts of protein in the urine. Because the GFR is normal, a patient in this early stage of chronic kidney disease will most likely be asymptomatic. As such, the majority of patients will only find out they’re in stage 1 if they’re being tested for other conditions such as diabetes or high blood pressure.
Stage 2 is characterized by kidney damage with mild loss of renal function, and is associated with a GFR between 60 and 89 millilitres per minute, and proteinuria for 3 months or more. In order to slow down the damage being done to the kidneys, patients are advised to eat a healthy diet and maintain a healthy weight, refrain from smoking or using tobacco, control both blood pressure and blood sugar, and engage in 30 minutes of exercise 5 days per week.
Stage 3 is characterized by mild to severe loss of renal function, and is associated with a GFR between 30 and 59 millilitres per minute. This stage is further separated into two substages, stage 3a and stage 3b. Stage 3a is for patients with a GFR between 45 and 59 millilitres per minute, while stage 3b is for patients with a GFR between 30 and 44 millilitres per minute. Many people in stage 3 will not have any symptoms, but those who do may experience frequent or infrequent urination, swelling in the hands and feet, or back pain. Health complications are also likely, such as high blood pressure, bone disease, and anemia.
Stage 4 is characterized by severe loss of renal function, and is associated with a GFR between 15 and 29 millilitres per minute. The symptoms and health complications are very similar to those of stage 3, as waste continues to build up in the body. Patients in stage 4 should schedule regular appointments with a nephrologist, meet with a dietitian, and take blood pressure medicines like ACE inhibitors and ARBs. It may also be time to prepare for both dialysis and a kidney transplant.
Stage 5 refers to end-stage renal disease, and is associated with a GFR that is less than 15 millilitres per minute. Symptoms of kidney failure include itching, back pain, muscle cramps, throwing up, frequent or infrequent urination, trouble sleeping and breathing, swelling in the hands and feet, and loss of appetite. Patients in this stage will be receiving dialysis regularly and will be a candidate for a kidney transplant.