Determining if You Have Kidney Disease
You have kidney disease if you meet either of two criteria: (1) estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m² OR (2) urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, with either abnormality persisting for at least 3 months. 1, 2
Diagnostic Criteria
Chronic kidney disease (CKD) is defined by persistent abnormalities in kidney structure or function lasting more than 3 months 1, 3. You need laboratory testing to make this diagnosis—kidney disease is typically asymptomatic in early stages, and most patients are unaware they have it 4, 3.
Two Primary Markers Define CKD:
Reduced Kidney Function:
- eGFR <60 mL/min/1.73 m² indicates loss of half or more of normal kidney function 1
- This threshold marks the point where complications of CKD increase substantially 1
- Normal eGFR in young adults is approximately 120-130 mL/min/1.73 m² and declines with age 1
Kidney Damage (Albuminuria):
- UACR ≥30 mg/g in a random spot urine sample indicates abnormal albumin excretion 1, 2
- Persistent proteinuria is the principal marker of kidney damage 1, 5
- Foamy urine often suggests proteinuria and warrants testing 5
Required Testing Algorithm
Step 1: Obtain baseline measurements 1, 2
Step 2: Confirm chronicity 1
- Repeat abnormal tests after 3 months 1
- If duration >3 months with persistent abnormalities, CKD is confirmed 1
- If duration unclear or <3 months, you may have acute kidney disease instead 1
Step 3: Stage the disease if CKD confirmed 1
- Stage 1: eGFR ≥90 with kidney damage markers
- Stage 2: eGFR 60-89 with kidney damage markers
- Stage 3a: eGFR 45-59
- Stage 3b: eGFR 30-44
- Stage 4: eGFR 15-29
- Stage 5 (kidney failure): eGFR <15 or requiring dialysis 1
Who Should Be Tested
High-risk populations requiring screening: 1, 2
- Diabetes (the leading cause of CKD, accounting for 30-40% of cases) 2
- Hypertension (another leading cause) 2
- Age >60 years 2
- Family history of kidney disease 2
- Cardiovascular disease 2
- Obesity 2
Critical Pitfalls to Avoid
Do not rely on serum creatinine alone—it misses early kidney disease because creatinine doesn't rise until significant kidney function is lost 1. Always calculate eGFR using a validated equation 1.
Do not assume normal kidney size on imaging excludes CKD—diabetic kidney disease, minimal change disease, and early focal segmental glomerulosclerosis commonly present with normal-sized kidneys despite progressive dysfunction 2.
Do not infer cause from comorbidities alone—up to 30% of patients with diabetes have other causes of CKD on kidney biopsy 2. The cause should be systematically evaluated, not assumed 1.
Do not wait for symptoms—CKD is asymptomatic until advanced stages 4, 3. By the time symptoms appear (uremia), you typically have stage 5 kidney failure 1.
When to Refer to Nephrology
Immediate referral criteria: 2, 5
- eGFR <30 mL/min/1.73 m² 2, 5
- Continuously increasing urinary albumin levels 2, 5
- Continuously decreasing eGFR 2, 5
- Rapid decline in eGFR (>10 mL/min/year with macroalbuminuria) 2
Management Implications Once Diagnosed
If you have CKD, treatment focuses on slowing progression and reducing cardiovascular risk 3:
Blood pressure control: Target <130/80 mmHg, especially with albuminuria ≥300 mg/g 2
Renin-angiotensin system blockade: ACE inhibitors or ARBs for patients with UACR ≥300 mg/g and/or eGFR <60 2
SGLT2 inhibitors: Reduce CKD progression and cardiovascular events in patients with diabetes and CKD 2
Statin therapy: Indicated for cardiovascular risk reduction in all CKD patients 2
Avoid nephrotoxins: NSAIDs, certain antibiotics, and other potentially harmful medications 3