Kidney diseases are classified based on the GFR which can be estimated from the patient's serum creatinine, corrected for age, gender and ethnicity. If the GFR is under 60 ml/min/173 m2, the patient has kidney disease and no other criteria is needed to diagnose kidney disease.
If the GFR is over 60 ml/min/1,73 m2, the patient must have additional signs of kidney damage. These are mainly structural abnormalities seen on ultrasounds or pathalogical protein excretion in the urine.
Therefore, identifying a patient with kidney disease is simple and cheap. Serum levels of creatinine, microscopy of urine, and the albumin/creatinine ratio will identify the majority of patients with kidney disease.
Classification:
| Stage | GFR ml/min/1,73m2 | Description |
|---|---|---|
| 1 | >90 | Normal kidney function but with structural abnormalities or markers in the urin pointing toward kidney disease |
| 2 | 60-89 | Slightly reduced kidney function, structural abnormalities, or markers in the urin pointing toward kidney disease |
| 3A | 45-59 | Moderately reduced kidney function |
| 3B | 30-44 | MModerately reduced kidney function |
| 4 | 15-29 | Severely reduced kidney function |
| 5 | <15 | End-stage kidney disease |
In order to better classify patients, suffixes after the GFR-based staging are used to indicate proteinuria, transplanted kidneys and dependence on dialysis.
Suffixes:
| p | indicates significant proteinuria > 500 mg/day. Proteinuria is an independent risk factor for both the progression of the kidney disease and risk for cardiovascular disease. Significant proteinuria is therefore an indicator for patients with higher risk than those without proteinuria. |
| T | indicates that the patient has a kidney transplant. |
| D | indicates that the patient is undergoing dialysis and divides those in stage 5 who receive dialysis from those who do not. |
Examples:
Patient with GFR 50, significant proteinuria: Stage 3Ap
Transplanted patient with GFR 50 and significant proteinuria: Stage 3ATp