Definition of CKD according to KDIGO classification
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Now I have comprehensive data from multiple authoritative textbooks. Here is the full, detailed answer:
Definition of CKD - KDIGO Classification
Core Definition (KDIGO 2012)
CKD is defined as abnormalities of kidney structure or function, present for longer than 3 months, with implications for health.
Either of the following criteria must be present for >3 months (90 days):
| Criterion | Details |
|---|---|
| Markers of kidney damage | (see below) |
| Decreased GFR | GFR <60 mL/min/1.73 m² |
CKD can be diagnosed without knowledge of its cause.
Markers of Kidney Damage
Any ONE of the following satisfies the "kidney damage" criterion:
- Albuminuria - >30 mg/day (or equivalent: ACR >30 mg/g, >3 mg/mmol)
- Urine sediment abnormalities - hematuria, red cell casts, tubular cell casts
- Electrolyte and other abnormalities from tubular disorders (e.g., renal tubular acidosis, Fanconi syndrome)
- Pathologic abnormalities on kidney biopsy
- Imaging abnormalities - hydronephrosis, asymmetric kidneys, polycystic kidneys, stones, small echogenic kidneys
- History of kidney transplantation - transplant recipients are always classified as CKD regardless of GFR or other markers
CGA Staging System
KDIGO classifies CKD by Cause (C), GFR category (G), and Albuminuria category (A) - collectively known as "CGA staging."
GFR Categories (G)
| Stage | Description | GFR (mL/min/1.73 m²) |
|---|---|---|
| G1 | Normal or high | ≥90 |
| G2 | Mildly decreased | 60-89 |
| G3a | Mildly to moderately decreased | 45-59 |
| G3b | Moderately to severely decreased | 30-44 |
| G4 | Severely decreased | 15-29 |
| G5 | Kidney failure | <15 |
- G1 and G2 alone do NOT constitute CKD unless accompanied by a marker of kidney damage
- Kidney failure (ESKD) = GFR <15 mL/min/1.73 m² OR initiation of kidney replacement therapy (dialysis or transplantation)
Albuminuria Categories (A)
| Stage | Description | ACR (mg/g) | ACR (mg/mmol) |
|---|---|---|---|
| A1 | Normal to mildly increased | <30 | <3 |
| A2 | Moderately increased | 30-300 | 3-30 |
| A3 | Severely increased | >300 | >30 |
Prognosis Heat Map (KDIGO 2012)
The grid below shows CKD risk for progression - a key feature of the KDIGO system:
- Green - Low risk (G1-G2 + A1: if no other markers of kidney disease, this does NOT constitute CKD)
- Yellow - Moderately increased risk
- Orange - High risk
- Red - Very high risk
Key Points
- Duration is the critical separator: >3 months = CKD; ≤3 months = Acute Kidney Disease (AKD); within 7 days = AKI
- Normal GFR is ~120-130 mL/min/1.73 m² in young adults and declines ~1 mL/min/year after the third decade; thus >25% of individuals aged ≥70 have GFR <60 - whether this is "normal aging" or pathological CKD remains debated
- Both decreased GFR AND albuminuria are independently associated with increased cardiovascular disease risk and all-cause mortality
- End-stage kidney disease (ESKD) is the subset of G5 treated with dialysis or transplantation
Sources: National Kidney Foundation Primer on Kidney Diseases, 8e (Ch. 51); Brenner and Rector's The Kidney (Ch. 19); Campbell-Walsh-Wein Urology (Ch. 87) - all citing KDIGO 2012 Clinical Practice Guideline, Kidney Int Suppl 3(1):2012
Latest KDIGO update on CKD
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KDIGO 2024 CKD guideline update key changes recommendations
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KDIGO 2024 CKD guideline key changes eGFR cystatin C SGLT2 finerenone recommendations summary
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KDIGO 2024 CKD guideline key changes classification eGFR SGLT2 finerenone GLP1 blood pressure management
I now have comprehensive data. Here is the full summary:
KDIGO 2024 CKD Guideline - Key Updates
Published: April 2024 in Kidney International (Suppl 4S), updating the 2012 guideline. Full PDF | Executive Summary PMID: 38519239
Note (March 2026): KDIGO has formally initiated a focused update to Chapter 3 (delaying progression, medical management), specifically to address newer evidence on SGLT2i, GLP-1 therapies, and nonsteroidal MRAs in non-diabetic CKD - a question not fully answered by the 2024 document. This update is in progress as of mid-2026.
1. Classification - What Changed from 2012
The core CGA framework (Cause, GFR, Albuminuria) and the heat map are retained, but with refinements:
| Aspect | 2012 | 2024 Update |
|---|---|---|
| eGFR equation | CKD-EPI 2009 (included race variable) | Race-free CKD-EPI 2021 creatinine as standard |
| Cystatin C | Optional add-on | Actively promoted - combine creatinine + cystatin C for confirmatory or discordant cases |
| Measured GFR | Rarely mentioned | Use iohexol or other exogenous markers when eGFR is unreliable |
| Risk prediction | Heat map only | Heat map retained + risk prediction models (e.g., KFRE - Kidney Failure Risk Equation) now recommended |
| Screening | Targeted | Expanded - primary care, cardiology, endocrinology all responsible for CKD detection |
2. The Four Pillars of Medical Management
The 2024 guideline restructures treatment around four foundational therapy classes, representing the biggest clinical shift:
Pillar 1 - SGLT2 Inhibitors (Strongest New Recommendation)
| Population | Recommendation | Grade |
|---|---|---|
| T2DM + CKD, eGFR ≥20 | Start SGLT2i | 1A (strong, high evidence) |
| Non-diabetic CKD, eGFR ≥20 + ACR ≥200 mg/g OR heart failure | Start SGLT2i | 1A |
| CKD, eGFR 20-45 + ACR <200 mg/g | Consider SGLT2i | 2B |
| Key practice point | Continue even if eGFR dips below 20 after initiation (unless intolerance or dialysis begins) | - |
| Caution | Withhold during prolonged fasting, surgery, or critical illness (ketoacidosis risk) | - |
Pillar 2 - RAS Inhibitors (ACEi/ARB)
- Use maximum tolerated doses - not just any dose - to achieve trial-proven benefits
- Remain first-line for proteinuric CKD, diabetic nephropathy, and hypertension in CKD
- Do NOT combine ACEi + ARB (dual blockade is contraindicated)
Pillar 3 - Nonsteroidal MRAs (Finerenone)
- Finerenone (not spironolactone/eplerenone) added for adults with T2DM + CKD already on maximally tolerated RASi
- Based on FIDELIO-DKD and FIGARO-DKD trial data showing cardiovascular and kidney protection
- Non-diabetic CKD: evidence under review in the 2026 focused update
Pillar 4 - Statins / Lipid Management
- Statins recommended for adults with CKD ≥50 years or with high cardiovascular risk regardless of age
- Lipoprotein(a) [Lp(a)] - measure at least once; elevated levels guide prevention intensity
- No treat-to-target eGFR approach for lipids - use fixed-dose strategy
3. GLP-1 Receptor Agonists
- Long-acting GLP-1 RA recommended for T2DM + CKD who have not achieved glycemic targets on metformin + SGLT2i, or who cannot use those agents
- Meta-analysis of 6 RCTs (n=47,434) showed 21% reduction in composite kidney endpoint (HR 0.79, 95% CI 0.73-0.87) vs placebo
- Evidence in non-diabetic CKD is being assessed in the 2026 update
4. Blood Pressure
- Target: <120 mmHg systolic (standardized measurement) for most adults with CKD - a lower target than the 2012 guideline's <130/80
- Based on SPRINT trial data
- Caution in elderly and those with orthostatic hypotension
5. Other Notable Recommendations
| Topic | Recommendation |
|---|---|
| Metabolic acidosis | Treat with sodium bicarbonate (with or without dietary intervention) to slow CKD progression |
| Hyperuricemia | Treat symptomatic gout with xanthine oxidase inhibitors (1C); do NOT treat asymptomatic hyperuricemia to slow CKD (2D) |
| Protein intake | Low protein diet (0.6-0.8 g/kg/day) suggested for non-dialysis CKD; avoid high protein (>1.3 g/kg/day) in at-risk patients |
| Smoking | Counsel all CKD patients to stop smoking |
| Anaemia | Erythropoiesis-stimulating agents + iron; HIF-PHI (daprodustat, roxadustat) now available in some regions |
| CKD-MBD | Phosphate binders, vitamin D analogues, calcimimetics per GFR and lab values |
| Drug stewardship | Dedicated chapter on medication dose adjustment, contrast media use, and NSAID avoidance |
6. Scope and Population
- Covers adults and children with CKD
- Does NOT cover dialysis patients or kidney transplant recipients (separate KDIGO guidelines for those)
- Sensitive to international and resource-limited settings
- Incorporates patient partner input throughout development
What's Coming: 2026 Focused Update (Chapter 3)
KDIGO announced in March 2026 a targeted update addressing three clinical questions specifically for non-diabetic CKD:
- SGLT2i in non-diabetic CKD - expanded indications based on post-2024 trial data
- Nonsteroidal MRAs (finerenone) in non-diabetic CKD
- GLP-1 receptor agonists in non-diabetic CKD
This is driven by new cardiovascular and kidney outcomes trials that emerged after the 2024 document was finalized.
Source: KDIGO 2024 CKD Guideline, Kidney Int 2024;105(Suppl 4S) [PMID 38490803]; Executive Summary [PMID 38519239]; Cleveland Clinic Journal of Medicine 2025; KDIGO.org announcement March 2026
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