The Glomerular Filtration Rate (GFR) is the best measure of existing kidney function. This value estimates the volume of blood the kidneys filter per minute, indicating how well the organs remove waste products. Monitoring the GFR is the standard method doctors use to diagnose and track the progression of chronic kidney disease (CKD). When kidney function declines significantly, the GFR becomes the focus of the major decision point regarding the need for life-sustaining therapies like dialysis.
What GFR Measures and CKD Stages
The GFR quantifies the performance of the glomeruli, the tiny filtering units within the kidneys. A normal GFR for a healthy young adult is typically around 120 mL/min/1.73 m², though this rate naturally decreases with age. Since directly measuring this rate is complicated, healthcare providers rely on an estimated GFR (eGFR), calculated using blood creatinine levels, age, sex, and size.
Chronic Kidney Disease (CKD) is classified into five progressive stages based on the GFR value. Stage 1 indicates kidney damage is present despite a normal GFR (90 mL/min/1.73 m² or greater). Stage 3 represents a moderate reduction in function, with GFR falling between 30 and 59 mL/min/1.73 m².
The most severe stage is Stage 5, defined by a GFR below 15 mL/min/1.73 m², which is classified as End-Stage Kidney Disease (ESKD). At this stage, the kidneys have lost nearly all their ability to filter blood and regulate the body’s internal environment. This signals that a patient is a candidate for renal replacement therapy, including dialysis or transplantation.
The GFR Range for Dialysis Initiation
While a GFR below 15 mL/min/1.73 m² marks the formal designation of Stage 5 kidney failure, dialysis is rarely initiated at exactly that number. This threshold serves as the point when comprehensive discussions and preparations for dialysis should begin. Therapy usually starts when the GFR has further declined, commonly falling into the range of 5 to 10 mL/min/1.73 m².
Starting dialysis earlier, such as above 10 mL/min/1.73 m², does not offer a survival advantage for most patients. The goal is to safely delay the start of dialysis for as long as possible to maintain the patient’s quality of life without increasing health risks. For an asymptomatic and stable patient, treatment may be safely postponed until the GFR is as low as 5 to 7 mL/min/1.73 m².
The GFR of 10 mL/min/1.73 m² is often used as a planning benchmark, ensuring necessary steps, such as creating vascular access, are completed ahead of time. However, the lower end of this range is when the buildup of waste products usually begins to cause noticeable, severe symptoms. This clinical presentation, rather than the number alone, ultimately drives the decision to begin treatment.
Non-GFR Factors Influencing the Dialysis Decision
The decision to start dialysis is individualized, meaning the patient’s clinical condition often outweighs the specific GFR number. Doctors focus on the presence of uremia, which is the buildup of waste products and toxins in the bloodstream due to kidney failure. Uremic symptoms are the most common indication for initiating dialysis, even if the GFR is slightly higher than the typical initiation range.
Severe, persistent symptoms that do not respond to medication are clear triggers for treatment. These include intractable nausea, vomiting, and a severe loss of appetite leading to poor nutritional status and weight loss. The accumulation of excess fluid that cannot be managed by diuretics, often presenting as shortness of breath or edema, also necessitates immediate intervention.
Other serious complications requiring prompt dialysis include uremic pericarditis, which is inflammation of the sac around the heart, and uremic encephalopathy, manifesting as changes in mental status and confusion. Uncontrolled hypertension, severe metabolic acidosis, or dangerously high potassium levels (hyperkalemia) refractory to medical therapy also demand the immediate start of renal replacement therapy. The presence of these life-threatening symptoms indicates that the body can no longer tolerate the level of kidney failure.
Primary Types of Renal Replacement Therapy
Once the GFR requires intervention, several methods of renal replacement therapy are available to take over the kidney’s filtering function. The two primary forms of dialysis are Hemodialysis (HD) and Peritoneal Dialysis (PD). Both methods remove toxins and excess fluid from the body using different mechanisms.
Hemodialysis involves circulating the patient’s blood outside the body through an artificial kidney, called a dialyzer. Inside the dialyzer, the blood passes across a semi-permeable membrane, where waste products move out of the blood and into a specialized dialysis fluid via diffusion and ultrafiltration. This treatment is typically performed three times a week, either at a dedicated center or in the patient’s home.
Peritoneal Dialysis uses the patient’s own peritoneal membrane, the lining of the abdomen, as a natural filter. A sterile solution, called dialysate, is introduced into the abdominal cavity through a catheter. Waste products and fluid pass from the blood vessels into the dialysate, which is then drained and replaced with fresh solution. Kidney transplantation, which involves surgically implanting a healthy donor kidney, is considered the optimal form of renal replacement therapy, offering the best chance for a return to normal function.