The kidneys are a pair of organs located on either side of the spine, near the waist. They function as filters, removing waste products and excess water from the blood to produce urine. This process eliminates toxins and maintains a balanced internal environment.
The Glomerular Filtration Rate (GFR) indicates how well these organs are performing. This measurement reflects the volume of fluid filtered from the tiny blood vessels within the kidneys, called glomeruli, into the urine-collecting tubules per unit of time. GFR provides insight into kidney function and helps identify any potential impairment.
Understanding GFR and Kidney Disease Stages
Glomerular Filtration Rate (GFR) measures how efficiently the kidneys filter waste from the blood. A decreased GFR indicates that the kidneys are not functioning as they should, which can be a sign of kidney disease.
GFR is estimated (eGFR) using a simple blood test that measures creatinine levels, along with factors like age, sex, and race. Creatinine is a waste product from muscle activity, and its levels in the blood rise as kidney function declines. While measured GFR (mGFR) is possible, it is a complex process, making eGFR the standard for routine evaluation.
Chronic Kidney Disease (CKD) is categorized into five stages based on GFR values. Stage 1 indicates normal kidney function with a GFR of 90 mL/min/1.73m² or higher, but with other signs of kidney damage, such as protein in the urine. Stage 2, or mild CKD, has a GFR between 60 and 89 mL/min/1.73m², still with evidence of kidney damage.
As kidney disease progresses, GFR continues to decline. Stage 3, moderately decreased kidney function, is divided into 3A (GFR 45-59 mL/min/1.73m²) and 3B (GFR 30-44 mL/min/1.73m²). Stage 4 signifies severely decreased kidney function, with a GFR ranging from 15 to 29 mL/min/1.73m². Stage 5, often referred to as End-Stage Renal Disease (ESRD) or kidney failure, is characterized by a GFR below 15 mL/min/1.73m².
When Dialysis is Typically Considered
Dialysis is considered when a patient reaches Stage 5 Chronic Kidney Disease (CKD), which corresponds to a Glomerular Filtration Rate (GFR) below 15 mL/min/1.73m². At this point, the kidneys have lost most of their filtering capacity and can no longer adequately remove waste products and excess fluid from the blood. This leads to a buildup of toxins in the body, a condition known as uremia.
While a GFR below 15 mL/min/1.73m² is a significant indicator, it is not the sole determinant for starting dialysis. Current guidelines emphasize that the decision should not be based exclusively on the estimated GFR number. In some cases, particularly for asymptomatic patients with Stage 5 CKD, dialysis may be safely delayed until the GFR drops to as low as 5–7 mL/min/1.73m², provided there is careful medical supervision and patient education.
The Initiating Dialysis Early and Late (IDEAL) study demonstrated that starting dialysis at an earlier GFR (e.g., above 10 mL/min/1.73m²) did not offer a benefit in terms of morbidity or mortality compared to starting later (at 5–7 mL/min/1.73m²). This research has influenced current clinical practices, shifting the focus from a strict GFR number to a more comprehensive assessment of the patient’s overall health and symptoms. While a very low GFR signals severe kidney failure, the exact timing of dialysis initiation is a personalized decision made in collaboration with a nephrologist.
Other Factors Influencing Dialysis Decisions
Beyond the Glomerular Filtration Rate (GFR) value, other factors influence the decision to initiate dialysis. The presence and severity of symptoms related to kidney failure are primary considerations. Patients often experience:
- Overwhelming fatigue
- Persistent itching
- Swelling in the hands, feet, or face due to fluid retention
- Nausea, vomiting, loss of appetite, or a metallic taste in the mouth
- Shortness of breath due to fluid accumulation in the lungs
The patient’s overall health status is also evaluated. This includes assessing for complications from advanced kidney disease, such as fluid overload that cannot be managed with medication, or inflammation around the heart (pericarditis). Uncontrolled high blood pressure and significant electrolyte imbalances, such as high potassium levels or acidosis, are also urgent indicators that may necessitate dialysis.
A patient’s nutritional status is another important consideration. Unexplained weight loss in advanced Stage 5 CKD can be a poor prognostic sign and may indicate the need for dialysis to improve overall well-being. The patient’s quality of life and personal preferences are key in this shared decision-making process. The healthcare team, including the nephrologist, discusses the potential benefits of dialysis in alleviating symptoms and potential complications, ensuring the decision aligns with the patient’s individual needs and goals.
Overview of Dialysis Treatment Options
Two main types of dialysis are available: hemodialysis and peritoneal dialysis. Each method removes waste products and excess fluid from the blood when the kidneys can no longer perform this function adequately.
Hemodialysis involves filtering the blood outside the body using an artificial kidney machine. Blood is drawn from the patient, passed through a dialyzer that removes waste and excess fluid, and then returned to the body. This treatment is typically performed at a dialysis center three times a week, with each session lasting approximately four hours, though home hemodialysis options are also available for more frequent, shorter sessions.
Peritoneal dialysis utilizes the lining of the abdomen, called the peritoneum, as a natural filter. A special fluid, called dialysate, is introduced into the abdominal cavity through a surgically placed catheter. The dialysate absorbs waste products and excess fluid from the blood across the peritoneal membrane. After a dwell time, the fluid is drained and replaced with fresh dialysate. This method offers more flexibility as it can be performed at home, either manually throughout the day or overnight using an automated cycler.