What are the management and treatment options for a patient with impaired renal function?

Management of Impaired Renal Function

Based on the laboratory values showing Stage 3b chronic kidney disease (eGFR 15-23 mL/min/1.73m²) with significantly elevated creatinine (2.46-3.79 mg/dL) and BUN (26-54 mg/dL), immediate nephrology referral is mandatory, along with comprehensive assessment for CKD complications, medication adjustments, and close monitoring to prevent progression to end-stage renal disease. 1, 2

Immediate Assessment and Risk Stratification

• Screen urgently for CKD complications including electrolyte abnormalities (hyperkalemia, hyperphosphatemia), metabolic acidosis, anemia, and metabolic bone disease, as these are common with eGFR <30 mL/min/1.73m² 1, 2

• Measure spot urine albumin-to-creatinine ratio to quantify proteinuria, which determines blood pressure targets and predicts progression risk 1, 2

• Obtain complete metabolic panel, CBC, phosphorus, calcium, PTH, vitamin D, and bicarbonate levels to identify treatable complications 3, 1

• Review all medications immediately for nephrotoxic agents and renally-cleared drugs requiring dose adjustment 1, 2

Blood Pressure Management

• Target BP ≤130/80 mmHg if proteinuria ≥30 mg/24 hours, or ≤140/90 mmHg if proteinuria <30 mg/24 hours 1

• Initiate ACE inhibitor or ARB as first-line therapy if proteinuria >300 mg/24 hours, uptitrating to maximally tolerated doses 1, 2

• Do not discontinue ACE inhibitor/ARB if creatinine increases up to 30% from baseline, as this represents expected hemodynamic changes rather than kidney damage 1

• Monitor creatinine 1-2 weeks after initiating or increasing ACE inhibitor/ARB doses to ensure stability 1

Critical Medication Adjustments

• Immediately discontinue all NSAIDs, aminoglycosides, and other nephrotoxic agents as these accelerate CKD progression 1, 2

• Adjust all renally-cleared medications based on eGFR of 15-23 mL/min/1.73m², including antibiotics, oral hypoglycemics, and anticoagulants 3, 1

• For anticoagulation needs, use bortezomib-containing regimens or agents not requiring renal dose adjustment rather than standard dosing of renally-cleared drugs 3

• If contrast imaging is required, use isosmolar contrast agents and ensure adequate hydration before and after to minimize contrast-induced nephropathy 1

• Avoid metformin, SGLT2 inhibitors, and certain oral hypoglycemics at this level of renal function due to safety concerns 2

Monitoring Strategy

• Monitor every 2-4 weeks initially with serum creatinine, eGFR, electrolytes (especially potassium), bicarbonate, and proteinuria until stable 1, 2

• Check CBC every 1-3 months to screen for anemia of CKD, which typically develops when eGFR <30 mL/min/1.73m² 1, 2

• Monitor bone metabolism markers (calcium, phosphorus, PTH, vitamin D) every 3 months as secondary hyperparathyroidism develops with advanced CKD 1, 2

• Define disease progression as ≥25% decline in eGFR from baseline or change in GFR category, which mandates intensified treatment 1

Management of CKD Complications

Hyperkalemia Management

• Restrict dietary potassium to <2-3 g/day and discontinue potassium-sparing diuretics 1
• Consider patiromer or sodium zirconium cyclosilicate if hyperkalemia prevents optimal RAAS blockade 2

Metabolic Acidosis

• Initiate sodium bicarbonate supplementation if serum bicarbonate <22 mEq/L, targeting 23-29 mEq/L to slow CKD progression 2

Anemia

• Initiate erythropoiesis-stimulating agents if hemoglobin <10 g/dL after excluding other causes and ensuring adequate iron stores 2

Mineral Bone Disease

• **Restrict dietary phosphorus to <800-1000 mg/day** and initiate phosphate binders if serum phosphorus >4.5 mg/dL 2
• Supplement vitamin D if 25-OH vitamin D <30 ng/mL to prevent secondary hyperparathyroidism 2

Nephrology Referral Criteria

• Refer immediately to nephrology as eGFR 15-23 mL/min/1.73m² represents Stage 3b-4 CKD with high risk of progression to end-stage renal disease 1, 2

• Urgent referral is indicated for eGFR <30 mL/min/1.73m², albuminuria ≥300 mg/24 hours, or rapid eGFR decline (>5 mL/min/1.73m² per year) 2

• Nephrology co-management is essential for renal replacement therapy planning, vascular access placement timing, and transplant evaluation 1, 2

Lifestyle Modifications

• Restrict sodium to <2 g/day to optimize blood pressure control and reduce proteinuria 1, 2

• Target BMI 20-25 kg/m² through dietary modification and regular exercise as tolerated 1

• Implement smoking cessation as smoking accelerates CKD progression 1

• Restrict protein intake to 0.8 g/kg/day in non-dialysis CKD to reduce uremic toxin accumulation 2

• Ensure adequate hydration while avoiding volume overload, particularly if concurrent heart failure exists 4

Common Pitfalls to Avoid

• Do not rely solely on serum creatinine as it has poor sensitivity for detecting renal dysfunction, especially in elderly or low muscle mass patients; always use eGFR 1, 5

• Do not withhold ACE inhibitor/ARB due to mild creatinine increases up to 30%, as this represents expected hemodynamic changes that provide long-term renoprotection 1

• Do not assume stable creatinine means stable kidney function in the setting of acute illness, dehydration, or new medications; reassess renal function immediately 3, 4

• Do not delay nephrology referral hoping for spontaneous improvement at this level of renal impairment, as early specialist involvement improves outcomes 1, 2

• Recognize that patients with Stage 3b-4 CKD have lost significant renal reserve and are at high risk for acute-on-chronic kidney injury from dehydration, infections, or nephrotoxic exposures 3, 4