What is the recommended management of proteinuria in a patient with an estimated glomerular filtration rate (eGFR) below 18 mL/min/1.73 m²?

Management of Proteinuria in eGFR <18 mL/min/1.73 m²

Continue ACE inhibitors or ARBs at the highest tolerated dose unless symptomatic hypotension, uncontrolled hyperkalemia, or worsening uremic symptoms occur, and consider reducing the dose or discontinuing only in these specific circumstances 1.

Primary Pharmacologic Management

RAS Inhibition Strategy

At eGFR <18 mL/min/1.73 m², you are managing advanced CKD (G5), and the approach differs from earlier stages:

• Continue existing ACEi/ARB therapy even at this severely reduced eGFR, as the 2024 KDIGO guidelines explicitly state to continue these agents even when eGFR falls below 30 mL/min/1.73 m² 1
• Use the highest approved dose tolerated to maximize antiproteinuric benefit 1
• Reduce dose or discontinue only if:
  • Symptomatic hypotension develops
  • Hyperkalemia remains uncontrolled despite medical management
  • Uremic symptoms worsen and need reduction while treating kidney failure at eGFR <15 1

Critical monitoring parameters: Check BP, serum creatinine, and potassium within 2-4 weeks of any dose adjustment 1. Accept up to 30% creatinine rise within 4 weeks—only discontinue if the rise exceeds this threshold 1.

SGLT2 Inhibitor Considerations

Do not initiate SGLT2 inhibitors at eGFR <20 mL/min/1.73 m² 1. However, if the patient is already on an SGLT2i that was started at eGFR ≥20, it is reasonable to continue it even as eGFR falls below 20, unless kidney replacement therapy is initiated or the medication is not tolerated 1.

Nonsteroidal MRA

**Nonsteroidal mineralocorticoid receptor antagonists are contraindicated at eGFR <18**, as the 2024 KDIGO guidelines recommend them only for eGFR >25 mL/min/1.73 m² 1.

Hyperkalemia Management

Aggressively manage hyperkalemia with potassium-lowering measures rather than stopping RASi 1. This includes:

• Dietary potassium restriction
• Potassium binders (patiromer, sodium zirconium cyclosilicate)
• Loop diuretics if volume overloaded
• Correction of metabolic acidosis

Only reduce or stop ACEi/ARB if hyperkalemia remains uncontrolled despite these interventions 1.

Dietary Protein Restriction

Implement low-protein diet of 0.6-0.8 g/kg/day at this advanced stage 2. This approach:

• Reduces proteinuria, particularly in non-diabetic CKD
• May increase serum albumin in hypoalbuminemic patients
• Helps defer dialysis initiation by decreasing nitrogen waste, metabolic burden, and phosphorus load 2

Ensure adequate energy intake of 30-35 kcal/kg/day and include at least 50% high-biologic-value protein to prevent protein-energy wasting 2. Consider supplementation with essential amino acids or ketoanalogues if protein intake drops below 0.6 g/kg/day 2.

Common Pitfalls to Avoid

1. Do not prematurely discontinue ACEi/ARB based solely on low eGFR—the guideline explicitly supports continuation at eGFR <18 unless specific complications arise 1
2. Do not use combination RAS blockade (ACEi + ARB, or either with direct renin inhibitor)—this is contraindicated 1
3. Do not stop RASi for hyperkalemia without first attempting medical management of the elevated potassium 1
4. Do not accept creatinine rises >30% within 4 weeks of RASi initiation or dose increase—this warrants discontinuation 1

Preparation for Kidney Replacement Therapy

At eGFR <18, simultaneously prepare for kidney replacement therapy while optimizing medical management. The proteinuria management serves dual purposes: slowing any remaining progression and reducing cardiovascular risk until dialysis or transplantation becomes necessary.