Stage 3a Chronic Kidney Disease
A GFR of 55 mL/min/1.73 m² corresponds to Stage 3a chronic kidney disease, defined as mildly to moderately decreased kidney function with a GFR range of 45-59 mL/min/1.73 m². 1
CKD Staging Classification
The KDIGO classification system stratifies chronic kidney disease by estimated glomerular filtration rate as follows: 1, 2
- Stage 1: ≥90 mL/min/1.73 m²
- Stage 2: 60-89 mL/min/1.73 m²
- Stage 3a: 45-59 mL/min/1.73 m² (your patient is here)
- Stage 3b: 30-44 mL/min/1.73 m²
- Stage 4: 15-29 mL/min/1.73 m²
- Stage 5: <15 mL/min/1.73 m² (kidney failure)
Diagnostic Confirmation Requirements
Chronic kidney disease diagnosis requires persistent abnormalities for at least three months; a single eGFR measurement is insufficient. 2 You must repeat the eGFR measurement within 2-4 weeks to differentiate acute kidney injury from chronic kidney disease. 3
If the creatinine-based eGFR appears discordant with the clinical picture, measure cystatin C-based eGFR for confirmation, as creatinine estimates are inaccurate in approximately 16-20% of individuals with eGFR <60 mL/min/1.73 m². 4, 2 The KDIGO guidelines specifically recommend using cystatin C when eGFR based on creatinine is 45-59 mL/min/1.73 m² and there are no other markers of kidney damage. 1
Clinical Significance and Risk Stratification
Stage 3a represents "mildly to moderately decreased" kidney function, but the actual risk depends critically on albuminuria status. 1 Stage 3a with normal albuminuria (A1) represents moderately high risk, while stage 3a with severe albuminuria (A3) represents high risk for progression and cardiovascular events. 1
As renal function declines below 60 mL/min/1.73 m², the prevalence of complications including anemia, malnutrition, bone disease, and neuropathy rises. 1 The prevalence of atrial fibrillation increases by 32% for those with an eGFR of 30-59 mL/min/1.73 m² compared to those with normal kidney function. 4
Mandatory Clinical Actions at Stage 3a
Initial Assessment
Obtain a spot urine albumin-to-creatinine ratio (ACR) immediately to stratify kidney disease risk and guide treatment intensity. 3 If abnormal, repeat testing on two of three separate specimens collected over 3-6 months to confirm the result. 3
Measure baseline serum potassium, hemoglobin, calcium, phosphate, and bicarbonate to screen for CKD-related complications that become common when eGFR falls below 60 mL/min/1.73 m². 3
Blood Pressure Management
Target systolic blood pressure <130 mmHg (but not <120 mmHg) for all adults with CKD and hypertension, supported by strong evidence from the SPRINT trial. 3 Blood pressure control and interventions to slow progression should be intensified at this stage. 1
If ACR ≥30 mg/g, start an ACE inhibitor or ARB immediately as first-line therapy, even when blood pressure is within target, because of blood pressure-independent nephroprotection. 3 Re-check serum creatinine and potassium 2-4 weeks after initiating or up-titrating an ACE inhibitor/ARB. 3
Nephroprotective Medications
If ACR ≥200 mg/g, start an SGLT2 inhibitor (empagliflozin, canagliflozin, or dapagliflozin) immediately if eGFR ≥20 mL/min/1.73 m², as these reduce CKD progression and cardiovascular events with Level 1A evidence. 3 An initial reversible eGFR decline of 2-3 mL/min/1.73 m² within the first 2 weeks is expected and does not require discontinuation. 3
For patients with diabetes and ACR 30-199 mg/g, start an SGLT2 inhibitor (Level 1A recommendation). 3 Consider a non-steroidal mineralocorticoid receptor antagonist (finerenone) if eGFR >25 mL/min/1.73 m², potassium is normal, and albuminuria persists despite maximally tolerated ACE inhibitor/ARB. 4, 3
Medication Management
Review and adjust doses of all renally cleared medications, as many require modification when eGFR is <60 mL/min/1.73 m². 3 NSAIDs should be strictly avoided, as they reduce renal blood flow and can precipitate acute kidney injury. 2 The "triple whammy" (NSAID + ACE inhibitor/ARB + diuretic) markedly increases acute kidney injury risk. 3
Dietary Modifications
Limit dietary protein to approximately 0.8 g/kg body weight per day to reduce hyperfiltration injury and slow progression. 2, 3 Restrict sodium to <2 g/day to reduce blood pressure and maximize diuretic effectiveness if needed. 2
Monitoring Schedule
Measure eGFR and urine albumin-to-creatinine ratio at least annually. 4, 3 Monitor serum potassium, hemoglobin, calcium, phosphate, and bicarbonate every 6-12 months to identify anemia, mineral-bone disorder, and metabolic acidosis. 3
Nephrology Referral Considerations
Nephrology consultation is not mandatory at stage 3a but should be considered, particularly if there is evidence of progression or complications. 1 Refer promptly to nephrology if there is uncertainty about etiology of kidney disease, difficult management issues, or rapidly progressing kidney disease (eGFR decline >5 mL/min/1.73 m² per year). 2, 3
Refer when ACR ≥300 mg/g, especially if there is a progressive increase. 3
Critical Pitfalls to Avoid
**Do not discontinue ACE inhibitor/ARB for creatinine rises <30% unless there is clear volume depletion**; stopping eliminates nephroprotection. 3 Continue ACE inhibitor/ARB unless serum creatinine rises >30% within 4 weeks; smaller rises are expected hemodynamic changes. 3
Do not stop an SGLT2 inhibitor because of the expected initial eGFR dip of 2-3 mL/min/1.73 m². 3 Continue the SGLT2 inhibitor even if eGFR falls below 20 mL/min/1.73 m², unless the drug is not tolerated or the patient initiates dialysis. 3
Always calculate eGFR using validated equations (CKD-EPI or MDRD) rather than relying on serum creatinine alone. 3 Serum creatinine concentration alone should not be used to assess kidney function. 2
Educate patients on "sick-day rules": temporarily hold ACE inhibitor/ARB, diuretics, and SGLT2 inhibitors during acute illnesses with volume depletion. 3 Withhold SGLT2 inhibitors during prolonged fasting, surgery, or critical illness due to the risk of ketoacidosis. 3