Overview.
Chronic kidney disease (CKD) is defined as abnormal kidney structure or function persisting for more than 3 months. It affects approximately 15% of US adults (~37 million people), but awareness is remarkably low — over 90% of those with early CKD are undiagnosed. CKD is staged using the KDIGO framework combining eGFR (filtration rate) and albuminuria (protein leak), which together predict progression risk and guide treatment decisions.
CKD represents a spectrum of kidney impairment from mild filtration decline (Stage G2) to kidney failure requiring dialysis or transplant (Stage G5). The kidneys filter ~180 litres of blood daily, regulate electrolytes, blood pressure, red blood cell production, and bone metabolism. As nephrons are lost, these functions progressively fail. The two most common causes — diabetes and hypertension — account for approximately 70% of cases.
Prevalence: ~15% of US adults (~37 million). Prevalence increases steeply with age: 6% at age 40-59, 25% at age 60-69, and >40% at age 70+. Diabetes and hypertension are the leading causes globally. Over 90% of people with Stage G1-G3a CKD are unaware of their diagnosis.
Medical name: Chronic Kidney Disease (CKD)
Symptoms.
Early warnings
- eGFR declining on routine blood work (even if still >60)
- Persistent proteinuria (foamy urine)
- Unexplained elevated creatinine
- Difficult-to-control hypertension (may be both cause and consequence)
- Recurrent gout (impaired uric acid clearance)
- Unexplained anaemia (reduced erythropoietin production)
Classic symptoms
- Early CKD (Stages G1-G3a): COMPLETELY ASYMPTOMATIC in most patients
- Moderate CKD (Stage G3b-G4): Fatigue, nocturia (frequent urination at night), mild oedema
- Advanced CKD (Stage G4-G5): Nausea, loss of appetite, metallic taste
- Pruritus (itching) from uraemia
- Peripheral oedema (swollen ankles)
- Shortness of breath (fluid overload or anaemia)
- Muscle cramps and restless legs
- Cognitive impairment ('uraemic fog')
Progression
CKD progression is measured by eGFR decline rate. Normal age-related decline: ~1 mL/min/year after age 40. Pathological decline: >5 mL/min/year warrants urgent evaluation. Diabetic kidney disease typically progresses through hyperfiltration → microalbuminuria → macroalbuminuria → declining eGFR → kidney failure over 15-25 years. SGLT2 inhibitors, ACE inhibitors/ARBs, and blood pressure control can dramatically slow this trajectory.
Risk factors.
- Diabetes mellitus (leading cause — 40% of CKD)
- Hypertension (second leading cause — 28% of CKD)
- Age >60
- Family history of kidney disease or kidney failure
- Obesity and metabolic syndrome
- Cardiovascular disease
- Chronic NSAID use (ibuprofen, naproxen)
- Recurrent urinary tract infections or kidney stones
- Autoimmune conditions (lupus, vasculitis)
- African American, Hispanic, or Native American ancestry
- History of acute kidney injury (AKI)
- Smoking
Lab interpretation.
Key biomarkers
- Serum Creatinine / eGFR — eGFR <60 mL/min sustained for ≥3 months defines CKD; staging from G1 (≥90) to G5 (<15) (primary)
- Urine Albumin:Creatinine Ratio (UACR) — A1 (<30 mg/g) normal; A2 (30-300) moderately elevated; A3 (>300) severely elevated (primary)
- Haemoglobin — Declining in CKD Stage G3b+ due to reduced erythropoietin production (renal anaemia) (secondary)
- Potassium — Rising in advanced CKD; hyperkalaemia risk increases with ACE/ARB use and eGFR <30 (secondary)
- Serum Albumin — Declining in nephrotic syndrome and advanced CKD (protein loss + malnutrition) (supportive)
Diagnostic criteria
- eGFR <60 mL/min/1.73m² sustained for ≥3 months (regardless of albuminuria)
- OR UACR ≥30 mg/g sustained for ≥3 months (regardless of eGFR)
- OR structural kidney abnormality (imaging: small kidneys, polycystic kidneys, single kidney)
- KDIGO staging uses BOTH eGFR (G1-G5) and albuminuria (A1-A3) together
- A single abnormal eGFR or UACR must be confirmed on repeat testing ≥3 months later before diagnosing CKD
- CKD-EPI 2021 equation (race-free) is the recommended eGFR calculation
Recommended panels
When & next steps.
When to test
- Diabetes mellitus (annual eGFR + UACR per ADA guidelines)
- Hypertension (annual screening)
- Age >60 with any cardiovascular risk factor
- Family history of kidney disease
- Long-term NSAID or nephrotoxic medication use
- Heart failure or coronary artery disease
- Recurrent kidney stones or UTIs
- Autoimmune conditions (lupus, rheumatoid arthritis)
If suspected
- Check eGFR (from serum creatinine using CKD-EPI 2021 equation)
- Check urine albumin:creatinine ratio (UACR) — spot urine, first morning void preferred
- If either is abnormal: repeat in 3 months to confirm chronicity
- Consider cystatin C-based eGFR if muscle mass confounders (bodybuilders, amputees, elderly, vegetarians)
- Renal ultrasound if cause is unclear (assess kidney size, obstruction, polycystic disease)
If confirmed
- Stage using KDIGO eGFR + albuminuria grid (determines prognosis and referral threshold)
- Blood pressure target <130/80 mmHg (KDIGO 2021)
- ACE inhibitor or ARB if UACR ≥30 mg/g (renoprotective, anti-proteinuric)
- SGLT2 inhibitor (dapagliflozin, empagliflozin) if eGFR ≥20 — renoprotective independent of diabetes status (DAPA-CKD, EMPA-KIDNEY trials)
- Avoid NSAIDs, limit contrast dye exposure
- Monitor potassium, phosphate, PTH, haemoglobin as eGFR declines
- Nephrology referral: eGFR <30, eGFR declining >5 mL/min/year, persistent UACR >300 mg/g, unclear aetiology
- Vaccination: hepatitis B if eGFR <30 (pre-dialysis vaccination is more effective)
FAQs.
I have Stage G3a CKD — does that mean I'll need dialysis?
Almost certainly not from CKD alone at this stage. Most people with Stage G3a (eGFR 45-59) never progress to dialysis, especially with good blood pressure control and avoiding nephrotoxins. The primary risk at Stage G3a is cardiovascular disease, not kidney failure. Progression to dialysis typically takes 10-20 years without intervention, and modern treatments (SGLT2 inhibitors, ACE/ARBs) dramatically slow decline.
Why is my eGFR declining even though I feel fine?
The kidneys have enormous reserve capacity. You can lose 50% of kidney function (eGFR from 100 to 50) before any symptoms appear. This is exactly why screening matters — by the time symptoms develop, significant irreversible damage has occurred. Annual eGFR + UACR screening catches problems when intervention is most effective.
Should I avoid protein to protect my kidneys?
Severe protein restriction is no longer routinely recommended for most CKD patients. Moderate protein intake (0.8 g/kg/day) is reasonable for Stage G3b+ to reduce uraemic toxin burden, but aggressive restriction risks malnutrition. In early CKD, normal protein intake is fine. Discuss with a renal dietitian.
What are SGLT2 inhibitors and should I be on one?
SGLT2 inhibitors (dapagliflozin, empagliflozin) were originally diabetes drugs but are now proven to slow CKD progression regardless of diabetes status. The DAPA-CKD and EMPA-KIDNEY trials showed ~30-40% reduction in kidney failure risk. If you have CKD with eGFR ≥20, discuss with your doctor — these are now considered standard of care.