What stage of chronic kidney disease (CKD) is a patient with a history of hypertension (HTN) and previous stage 3 CKD now in with a creatinine level of 2.3 and estimated glomerular filtration rate (eGFR) of 31?

CKD Stage Classification

Your patient is now in Stage 3b chronic kidney disease, having progressed from Stage 3 (which encompasses both 3a and 3b) to specifically Stage 3b based on the current eGFR of 31 mL/min/1.73 m².

Staging Criteria

The National Kidney Foundation K/DOQI classification system defines CKD stages based on eGFR values 1, 2:

• Stage 3a: eGFR 45-59 mL/min/1.73 m² 2
• Stage 3b: eGFR 30-44 mL/min/1.73 m² 2
• Stage 4: eGFR 15-29 mL/min/1.73 m² 1, 2
• Stage 5: eGFR <15 mL/min/1.73 m² or kidney failure requiring dialysis 2

With an eGFR of 31 mL/min/1.73 m², your patient falls squarely into Stage 3b 2.

Clinical Significance of This Progression

This progression from Stage 3 to Stage 3b carries substantial clinical implications:

• Patients who progress from Stage 3 to Stage 4 (which your patient is approaching) have significantly higher adjusted risks of death (HR 2.56), acute kidney injury (HR 2.32), and all-cause hospitalization (HR 1.87) compared to those who remain stable 3
• The risk of CKD complications increases significantly below eGFR of 60 mL/min/1.73 m², and your patient is now well below this threshold 2
• At Stage 3b, systematic evaluation and treatment of CKD complications becomes the primary clinical action plan 2

Immediate Clinical Actions Required

Nephrology referral is strongly indicated at this stage:

• Patients with eGFR <30 mL/min/1.73 m² should be referred to nephrology 4
• While your patient is at 31 mL/min/1.73 m² (just above the absolute threshold), the combination of lifelong hypertension, one-year gap in monitoring, and proximity to Stage 4 warrants nephrology consultation 1, 4

Essential workup to perform immediately:

• Measure urinary albumin-to-creatinine ratio (UACR) on a random spot urine sample, as albuminuria classification is essential for risk stratification and determines monitoring frequency 1, 4
• Complete metabolic panel including electrolytes (sodium, potassium, bicarbonate) to screen for metabolic acidosis and hyperkalemia 4
• Complete blood count to assess for anemia 4
• Serum calcium, phosphate, intact PTH, and 25-hydroxyvitamin D to evaluate for mineral bone disease, as PTH begins rising when eGFR falls below 60 mL/min/1.73 m² 4
• Lipid panel for cardiovascular risk assessment 4

Common Pitfalls to Avoid

• Do not rely on serum creatinine alone—always calculate eGFR using validated equations 4
• Do not skip albuminuria testing, as eGFR and UACR provide independent prognostic information for cardiovascular events, CKD progression, and mortality 4
• Do not assume stable disease just because the patient feels well—CKD at this stage is typically asymptomatic 2
• Be aware that CKD progression can be nonlinear and unpredictable, with some patients experiencing rapid decline following acute kidney injury events 5

Monitoring Frequency

The monitoring frequency depends on albuminuria status 4:

• If UACR <30 mg/g: monitor 2 times per year 4
• If UACR 30-300 mg/g: monitor 3 times per year 4
• If UACR >300 mg/g: monitor 4 times per year and ensure nephrology referral 4