Stages of Kidney Failure: Understanding GFR and Chronic Kidney Disease Classification
Kidney failure, a serious medical condition affecting millions worldwide, is primarily assessed through key indicators such as serum creatinine levels and the glomerular filtration rate (GFR). These markers help clinicians determine the severity of kidney dysfunction and guide appropriate treatment strategies. Kidney failure is broadly categorized into two types: acute kidney injury (AKI) and chronic kidney disease (CKD). While AKI develops rapidly over hours or days, CKD progresses slowly over months or years, often going unnoticed until significant damage has occurred.
The Traditional Staging of Kidney Function Decline
In earlier medical practice, kidney function was classified into four main phases based on functional capacity: renal compensation, decompensation, kidney failure, and uremic stage. During the compensatory phase, the kidneys begin to lose efficiency, yet they still manage to maintain overall bodily balance. This stage typically corresponds to a GFR between 50 and 80 mL/min, where patients may not exhibit noticeable symptoms.
As kidney function deteriorates further, it enters the decompensated phase, with GFR dropping to 26–50 mL/min. At this point, waste products start accumulating in the blood, leading to early signs like fatigue, mild swelling, or changes in urination patterns. The next critical phase—kidney failure—is marked by a GFR of 10–25 mL/min, indicating severe impairment and requiring close monitoring and lifestyle adjustments.
The final and most severe stage, known as the uremic phase, occurs when the GFR falls below 10 mL/min. In this state, the body can no longer effectively filter toxins, resulting in systemic complications such as nausea, confusion, anemia, and fluid overload. Without intervention, this condition becomes life-threatening.
Modern Classification: Chronic Kidney Disease (CKD) Stages I–V
Today, the global medical community predominantly uses the five-stage model of chronic kidney disease (CKD), which provides a more standardized and clinically useful framework. This classification system is centered around estimated glomerular filtration rate (eGFR), measured in mL/min/1.73m², and helps doctors assess both kidney function and structural damage.
Stage I – Normal or High GFR with Kidney Damage
CKD Stage I reflects normal kidney function with an eGFR ≥90 mL/min. However, other signs—such as protein in the urine (proteinuria), hematuria, or imaging abnormalities—indicate underlying kidney damage. Early detection at this stage allows for interventions that may slow progression, including blood pressure control and diabetes management.
Stage II – Mild Reduction in GFR
In Stage II, the eGFR ranges from 60 to 89 mL/min. Although function appears relatively preserved, subtle declines combined with biomarkers of kidney injury suggest early-stage disease. Patients are often asymptomatic, making routine screening crucial for those at risk, especially individuals with hypertension, diabetes, or a family history of kidney disorders.
Stage III – Moderate Kidney Impairment
This stage is subdivided into IIIa (eGFR 45–59 mL/min) and IIIb (eGFR 30–44 mL/min). By this point, many patients begin experiencing symptoms such as swelling in the legs, fatigue, and increased nighttime urination. It's also a pivotal window for preventing rapid deterioration through dietary modifications, medication adjustments, and managing comorbidities.
Stage IV – Severe Reduction in Kidney Function
With an eGFR between 15 and 29 mL/min, Stage IV signifies advanced kidney disease. Patients usually require regular follow-ups with nephrologists and preparation for future renal replacement therapy. Discussions about dialysis options and transplant eligibility often begin during this phase to ensure timely care planning.
Stage V – End-Stage Renal Disease (ESRD)
When eGFR drops below 15 mL/min, the individual has reached end-stage renal disease (ESRD), equivalent to the traditional uremic phase. At this stage, the kidneys can no longer sustain basic physiological functions. Life-sustaining treatments become essential, including hemodialysis, peritoneal dialysis, or kidney transplantation. Each option comes with its own benefits and challenges, and patient-centered decision-making is vital.
Understanding these stages empowers patients and healthcare providers to act proactively. Regular testing, early diagnosis, and comprehensive management plans significantly improve quality of life and delay disease progression. As awareness grows and medical advancements continue, effective strategies for living well with kidney disease are more accessible than ever before.