2020 Nov 21. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan–.
Chronic kidney disease (CKD) is defined as the presence of kidney damage or an estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73 mt2, persisting for 3 months or more, irrespective of the cause. It is a state of progressive loss of kidney function ultimately resulting in the need for renal replacement therapy (dialysis or transplantation). Kidney damage refers to pathologic abnormalities either suggested by imaging studies or renal biopsy, abnormalities in urinary sediment, or increased urinary albumin excretion rates. The 2012 KDIGO CKD classification recommends details about the cause of the CKD and classifies into 6 categories based on glomerular filtration rate (G1 to G5 with G3 split into 3a and 3b). It also includes the staging based on three levels of albuminuria (A1, A2, and A3), with each stage of CKD being sub-categorized according to the urinary albumin-creatinine ratio in (mg/gm) or (mg/mmol) in an early morning “spot” urine sample.
The 6 categories include:
G1: GFR 90 ml/min per 1.73 m2 and above
G2: GFR 60 to 89 ml/min per 1.73 m2
G3a: GFR 45 to 59 ml/min per 1.73 m2
G3b: GFR 30 to 44 ml/min per 1.73 m2
G4: GFR 15 to 29 ml/min per 1.73 m2
G5: GFR less than 15 ml/min per 1.73 m2 or treatment by dialysis
The three levels of albuminuria include an albumin-creatinine ratio (ACR)
A1: ACR less than 30 mg/gm (less than 3.4 mg/mmol)
A2: ACR 30 to 299 mg/gm (3.4 to 34 mg/mmol)
A3: ACR greater than 300 mg/gm (greater than 34 mg/mmol).
The improved classification of CKD has been beneficial in identifying prognostic indications related to decreased kidney function and increased albuminuria. However, a downside of the use of classification systems is the possible overdiagnosis of CKD, especially in the elderly.