CKD is abnormalities of kidney structure or function, present for greater than or equal to 3 months and with implications for health. CKD is classified into 5 stages based on measured or estimated glomerular filtration rate (eGFR) (KDOQ1, 2002). KDIGO maintains the classification of CKD through staging as developed in the 2002 KDOQI guidelines with three notable changes: 1) the addition of cause, 2) the addition of albuminuria categories, and 3) separating stage 3 into two distinct stages. CKD Stage 1: Normal kidney function, but evidence of kidney damage with GFR greater than or equal to 90 mL/min/1.73 m². Stage 2: Mildly reduced kidney function and kidney damage with GFR 60-89 mL/min/1.73 m². Stage 3: Moderately reduced kidney function has been divided into Stage 3a (GFR 45-59 mL/min/1.732) and Stage 3b (GFR 30-44 mL/min/1.73m2) to more precisely reflect the risks of mortality and other outcomes. Stage 4: Severely reduced kidney function with GFR 15-29 mL/min/1.73 m². Stage 5: Kidney failure with GFR less than 15 mL/min/1.73 m².
Kidney Disease, Improving Global Outcomes (KDIGO). (2013). KDIGO 2012 Clinical practice guideline for evaluation and management of chronic kidney disease. Kidney International Supplements, 3 (1), 1-150.
National Kidney Foundation (2002). KDOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. American Journal of Kidney Disease, 39, S1-S266.