# CKD Staging: KDIGO 2024 Classification & Management Framework ## Use risk to plan the next service For eligible CKD G3–G5, a validated kidney-failure risk equation can supplement cause, eGFR, symptoms and trajectory. KDIGO 2024 uses a 5-year risk of 3–5% to help guide nephrology referral, a 2-year risk \>10% for multidisciplinary care, and \>40% for modality education and kidney-replacement preparation. These are decision aids, not automatic dialysis-start thresholds. Assess eGFR and albuminuria at least annually, more often at higher risk or after treatment changes; an eGFR change \>20% or ACR doubling merits evaluation. Consider combined creatinine–cystatin C estimation when accuracy changes the decision. [KDIGO 2024 CKD guideline](https://pubmed.ncbi.nlm.nih.gov/38490803/). ## KDIGO 2012 CKD Definition (Still Gold Standard) **Chronic Kidney Disease = kidney damage for ≥3 months manifested by:** 1. **Albuminuria** (any degree) OR 2. **GFR \<60 mL/min/1.73m² BSA** OR 3. **Abnormal kidney imaging** (cysts, fibrosis, scarring) Key Point **CKD is defined by abnormality, not by kidney disease diagnosis.** A patient with diabetes WITHOUT albuminuria or low GFR does NOT have CKD. ------------------------------------------------------------------------ ## KDIGO 2024 Staging: G Categories (GFR) + A Categories (Albuminuria) ### **GFR Categories (G1–G5)** | Category | GFR (mL/min/1.73m²) | Clinical Description | |----------|---------------------|----------------------------------| | **G1** | ≥90 | Normal or high | | **G2** | 60–89 | Mildly decreased | | **G3a** | 45–59 | Mildly-to-moderately decreased | | **G3b** | 30–44 | Moderately-to-severely decreased | | **G4** | 15–29 | Severely decreased | | **G5** | \<15 | Kidney failure (ESRD) | ### **Albuminuria Categories (A1–A3)** | Category | UACR (mg/g) | UPCR (g/day) | Clinical Risk | |----------|-------------|--------------|--------------------------------| | **A1** | \<30 | \<0.5 | Normal to mildly increased | | **A2** | 30–300 | 0.5–3.5 | Moderately increased | | **A3** | \>300 | \>3.5 | Severely increased (nephrotic) | Clinical Pearl **UACR conversion:** 1 g/day ≈ 1,000 mg/day - Spot UACR \>300 mg/g ≈ 24-h proteinuria \>3.5 g/day - **Nephrotic range proteinuria:** \>3.5 g/day (or UACR \>300) ------------------------------------------------------------------------ ## KDIGO 2024 Heat Map: Risk Stratification **New in 2024:** GFR + Albuminuria matrix creates color-coded risk: A1 (<30) A2 (30-300) A3 (>300) Green Yellow Orange/Red G1 (≥90) ✓ Green Yellow Orange G2 (60-89) ✓ Green Yellow Orange G3a (45-59) Yellow Yellow Orange G3b (30-44) Yellow Orange Red G4 (15-29) Orange Orange Red G5 (<15) Red Red Red **Interpretation:** - **Green (Low risk):** G1–G2 + A1; most don’t need nephrology referral - **Yellow (Moderate risk):** G3a-G3b ± A1, or G1–G2 + A2; monitor closely - **Orange (High risk):** G3b–G4 + A2, or any + A3; nephrology referral indicated - **Red (Very high risk):** G4–G5 ± any A; urgent nephrology Key Point **Nephrology referral threshold:** - **Urgent (same week):** G5 (Cr \>10 mg/dL), uncontrolled HTN, rapidly declining GFR - **Soon (within 2–4 weeks):** G3b + albuminuria, G4 ± albuminuria, CKD + diabetes - **Routine (within 3 months):** G3a + albuminuria, first CKD diagnosis ------------------------------------------------------------------------ ## GFR Estimation: CKD-EPI 2021 Equation **Modern standard:** CKD-EPI 2021 (replaces Cockcroft-Gault, MDRD) **Advantages:** - Includes cystatin C (more accurate in extremes) - Better at high GFR (overestimation reduced) - Racial demography removed (no longer uses “Black race multiplier”) - More accurate at low GFR **Formula components:** - **Serum creatinine** (Cr) — measured in μmol/L or mg/dL - **Cystatin C** (optional) — serum cystatin C in mg/L - **Age, sex** **Online calculator:** KDIGO.org (avoids arithmetic errors) Clinical Pearl **When CKD-EPI differs from MDRD:** - CKD-EPI ↑ GFR estimate → LESS overestimation of CKD severity - Pt with Cr 1.2 (MDRD eGFR 60) → CKD-EPI eGFR 65 (not CKD G3 by eGFR alone) - Always use SAME equation for trending; don’t mix calculators ### **Cystatin C Benefits** - Filtered freely, reabsorbed + catabolized (not reabsorbed like Cr) - Better marker in: elderly, sarcopenic patients, pregnancy, muscle wasting - Less affected by diet, muscle mass **Cystatin C GFR equation:** CKD-EPI 2012 (or newer 2021 with creatinine) ------------------------------------------------------------------------ ## Risk Factors for CKD Progression & Complications ### **Non-Modifiable** - Age \>60 - Male sex - Race/ethnicity (African American, Native American, Hispanic — multiple mechanisms, not purely genetic) - Family history of CKD or ESRD ### **Modifiable: THE BIG ONES** 1. **Diabetes (most common cause, ~1/3 of ESRD)** — tight glucose control (HbA1c \<7%), ACE-I/ARB 2. **Hypertension (2nd most common)** — BP target \<120 mmHg (SPRINT-CKD concept) 3. **Albuminuria** — reduced by ACE-I/ARB/SGLT2i/finerenone/GLP1-RA 4. **NSAIDs & other nephrotoxins** — avoid with advancing CKD 5. **Smoking** — increases proteinuria, HTN 6. **Poor diet** — sodium ↑, phosphate ↑, potassium ↑ 7. **Obesity** — association with progression ------------------------------------------------------------------------ ## Key Management by Stage ### **CKD G1–G2 with A1 (No referral)** - No kidney disease treatment required if no other indicator - Regular monitoring: Cr × 1 year, UA × 1 year - Modify traditional CV risk factors (HTN, lipids, smoking) ### **CKD G3a (45–59) ± Albuminuria (Routine referral)** - **If albuminuria:** ACE-I or ARB first-line - Monitor Cr, K, electrolytes 1–2 weeks after ACE-I start - Encourage DASH diet, weight loss, exercise - Target BP: \<120 mmHg systolic (SPRINT-CKD) ### **CKD G3b (30–44) with A2–A3 (Referral within 1 month)** - **Triple therapy:** ACE-I/ARB + SGLT2i + (finerenone or GLP1-RA if diabetic) - Monitor bone/mineral (Ca, PO4, PTH, 25-OH VitD) - Adjust drug dosing (renally cleared meds) - Prepare for advanced CKD counseling (dialysis, transplant, conservative) ### **CKD G4 (15–29) (Urgent referral)** - **Full nephrology co-management** - Advanced CKD clinic: vascular access creation, transplant eval, dialysis education - Bone-mineral-disorder (BMD) management: phosphate binders, vitamin D, calcimimetics - Anemia management: iron, ESA (if Hgb \<10 g/dL despite iron) - Cardiovascular risk reduction ### **CKD G5 (Cr \<15 or already on dialysis) (EMERGENT)** - **RRT initiation planning** (dialysis start or preemptive transplant) - Vascular access (fistula, graft) - Peritoneal access if PD choice - **RRT education** before GFR \<15 to optimize timing ------------------------------------------------------------------------ ## UACR & 24-Hour Urine Protein Interpretation ### **When to Order Each** - **Spot UACR:** Easiest, no 24-h collection needed; preferred for screening - **24-hour urine:** If discordant symptoms (dipstick 2+ but low UACR), large patient, high-protein diet, or research ### **UACR Thresholds** | UACR (mg/g) | Category | Action | |----|----|----| | \<30 | Normal/A1 | Reassure; recheck yearly | | 30–300 | Microalb/A2 | ACE-I/ARB; SGLT2i if DM | | \>300 | Macroalb/A3 | Urgent treatment; consider nephrotic workup if \>1 g/day | Clinical Warning **False high UACR:** Fever, UTI, menstruation, intense exercise, hypertension crisis **False low UACR:** Dilute urine (high urine volume) Repeat if markedly abnormal and clinically discordant. ------------------------------------------------------------------------ ## CKD-MBD (Mineral-Bone Disorder): Screening by Stage **Start mineral screening at G3a; more frequent at G3b–G5:** | Test | G1–G3a | G3b | G4 | G5 | |----|----|----|----|----| | **Serum Ca, PO4** | Yearly | Yearly | Q6 months | Monthly–Q6 weeks | | **PTH** | Once if G3a | Q12 months | Q3–6 months | Q3 months | | **25-OH Vitamin D** | Once | Once | Once | Q6–12 months | | **FGF23** | Rarely | If progression rapid | If progression rapid | Not routine | **Screening findings:** - **PTH \>100 pg/mL** at GFR 45–59 → Start vitamin D - **PO4 \>4.5 mg/dL** → Diet counseling + consider binders at G4 - **Ca-PO4 product \>55** → Risk of vascular calcification ------------------------------------------------------------------------ ## Referral Criteria Summary (Handy Chart) | Indication | Timing | |----------------------------------------------|-----------------| | CKD diagnosis (new) | Routine | | G3b + albuminuria | Within 1 month | | G4 ± albuminuria | Within 2 weeks | | G5 (ESRD) | URGENT same day | | Rapidly declining GFR (\>5 mL/min/year drop) | Urgent | | Uncontrolled HTN despite 3+ drugs | Urgent | | Protein \>3.5 g/day (nephrotic) | Urgent | | Abnormal kidney imaging | Within 1 month | ------------------------------------------------------------------------ ## Related Resources - Comprehensive CKD Staging Review - CKD Mineral-Bone Disorder - Diabetic Kidney Disease - Dialysis Initiation Planning - Renal Transplant Immunosuppression ------------------------------------------------------------------------ ## Self-Test Questions 1. **72M, Cr 1.5 (baseline 1.2), no albuminuria, BP 140/85 on HCTZ** - GFR estimate (CKD-EPI): ~48 mL/min (G3b) - Albuminuria category: A1 - Risk: Moderate-yellow (G3b + A1) - Action: ACE-I/ARB start, BP target \<120 2. **45F with DM, Cr 0.9, UACR 250 mg/g, BP 125/80 on lisinopril** - GFR: ~70 (G2) - Albuminuria: A2 - Risk: Moderate-yellow (G2 + A2) - Action: Add SGLT2i, target HbA1c \<7%, routine referral 3. **68M, Cr 2.8, K 5.8, PO4 5.2, PTH 180** - GFR: ~20 (G4) - Risk: Red (G4 + any A) - Action: Urgent nephrology, start BMD management, plan RRT ------------------------------------------------------------------------ *Version 1.0 \| PA/Medical student level \| Updated 2026-02-28* **References:** [KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD](https://pubmed.ncbi.nlm.nih.gov/38490803/); [Levey et al. A new equation to estimate glomerular filtration rate (2009)](https://pubmed.ncbi.nlm.nih.gov/19414839/). --- [Website version](https://urinenephrology.org/student-resources/ckd/ckd-staging-student-handout.html) · Markdown synchronized October 3, 2026.