Clinical meaning
The KDIGO classification stages CKD using a two-dimensional matrix combining GFR categories and albuminuria categories. GFR stages: G1 (≥90, normal), G2 (60-89, mildly decreased), G3a (45-59, mild-moderate), G3b (30-44, moderate-severe), G4 (15-29, severe), G5 (<15, kidney failure). Albuminuria categories: A1 (<30 mg/g, normal), A2 (30-300, moderately increased/microalbuminuria), A3 (>300, severely increased/macroalbuminuria). G1-G2 require evidence of kidney damage (albuminuria, structural abnormality) to qualify as CKD. The heat map assigns risk colors guiding monitoring frequency: green (annual), yellow (annual), orange (every 6 months), red (every 3 months). Management intensity increases with both declining GFR and increasing albuminuria.