Kidney Function Failure: Understanding Diagnosis Criteria and Staging Systems
Chronic kidney disease (CKD) is a progressive condition that, when left unmanaged, can lead to kidney function failure. Accurate diagnosis and staging are crucial for effective treatment planning and patient outcomes. Two widely recognized systems are used globally to assess the severity of kidney impairment: one based on serum creatinine levels commonly applied in certain regions, and another more universally adopted framework using estimated glomerular filtration rate (eGFR), as outlined by international guidelines such as KDIGO and K/DOQI.
Traditional Creatinine-Based Classification of Kidney Failure
In some clinical settings, particularly in certain regional medical practices, kidney function decline is categorized according to serum creatinine concentrations. This method divides chronic kidney failure into several distinct phases:
Compensatory Stage (Stage 1)
During the early compensatory phase, the kidneys still maintain adequate function despite underlying damage. Serum creatinine levels remain relatively low, typically below 133 μmol/L. At this stage, patients may not exhibit noticeable symptoms, making early detection challenging without routine blood tests.
Decompensated or Azotemic Stage (Stage 2)
As kidney function deteriorates, waste products begin to accumulate in the bloodstream—a condition known as azotemia. In this phase, creatinine levels rise to between 177 and 442 μmol/L. Patients may start experiencing fatigue, nausea, changes in urination patterns, and mild fluid retention.
Renal Failure Stage (Stage 3)
When creatinine reaches 442–707 μmol/L, the condition progresses to established renal failure. The kidneys are significantly impaired, and symptoms become more pronounced, often including hypertension, anemia, electrolyte imbalances, and reduced urine output.
End-Stage Renal Disease (ESRD) or Uremia (Stage 4)
The final stage occurs when creatinine exceeds 707 μmol/L, indicating end-stage kidney failure. At this point, dialysis or kidney transplantation becomes necessary for survival. Symptoms of uremia—such as confusion, itching, shortness of breath, and severe fatigue—are common and require immediate medical intervention.
Modern eGFR-Based Staging According to KDIGO/K/DOQI Guidelines
Today, most healthcare professionals rely on the KDIGO (Kidney Disease: Improving Global Outcomes) and K/DOQI (Kidney Disease Outcome Quality Initiative) guidelines, which use estimated glomerular filtration rate (eGFR) to classify CKD into five stages. This method provides a more accurate reflection of actual kidney function and allows for earlier detection and management.
Stage 1: Normal or High GFR with Kidney Damage
eGFR greater than 90 mL/min/1.73m², but with evidence of structural or functional kidney abnormalities (e.g., proteinuria or imaging findings). Early diagnosis at this stage enables preventive measures.
Stage 2: Mild Reduction in GFR
eGFR ranges from 60 to 89 mL/min/1.73m². While kidney function is only slightly reduced, continued monitoring is essential, especially in individuals with risk factors like diabetes or hypertension.
Stage 3: Moderate Decline in Kidney Function
This stage is further divided into 3a (eGFR 45–59) and 3b (eGFR 30–44). Overall, it represents a moderate reduction in filtration capacity (30–59 mL/min/1.73m²). Complications such as bone disorders and anemia may begin to emerge.
Stage 4: Severe Kidney Impairment
With eGFR between 15 and 29 mL/min/1.73m², patients are approaching end-stage disease. Comprehensive care planning—including evaluation for dialysis or transplant—is critical during this phase.
Stage 5: End-Stage Renal Disease (eGFR < 15)
When eGFR drops below 15 mL/min/1.73m², kidney replacement therapy (dialysis or transplantation) is required. Without intervention, life-threatening complications due to toxin buildup and fluid overload will occur.
Understanding these diagnostic criteria empowers both clinicians and patients to take proactive steps in managing kidney health. Regular screening, especially for those with diabetes, high blood pressure, or a family history of kidney disease, can significantly improve long-term outcomes. As global standards continue to evolve toward eGFR-based assessment, early detection and personalized treatment plans are becoming more accessible than ever.