How is proteinuria managed in primary care in an adult patient with impaired renal function, as indicated by a creatinine level of 75, and without specified comorbidities?

Management of Proteinuria in Primary Care with Creatinine 75 µmol/L

In a patient with a creatinine of 75 µmol/L (approximately 0.85 mg/dL, indicating preserved renal function) and proteinuria, primary care management should focus on quantifying the proteinuria, initiating ACE inhibitor or ARB therapy if proteinuria exceeds 0.5-1 g/day, implementing cardiovascular risk reduction strategies, and determining whether nephrology referral is needed based on the degree of proteinuria. 1, 2

Initial Assessment and Quantification

• Quantify proteinuria using a spot urine protein-to-creatinine ratio (PCR) or albumin-to-creatinine ratio (ACR) on an early morning sample, confirming any positive result with repeat measurement within 3 months. 1, 3

• Calculate eGFR using the CKD-EPI equation and document blood pressure at initial presentation, as these directly impact risk stratification and treatment targets. 3

• Perform renal ultrasound to assess kidney size (small kidneys <9 cm suggest advanced disease), rule out obstruction, and identify structural abnormalities. 1, 2, 3

• Order serological testing including hepatitis B and C serologies, complement levels, antinuclear antibody, quantitative immunoglobulins, serum and urine protein electrophoresis, and cryoglobulin levels to identify secondary causes. 2, 3

Treatment Algorithm Based on Proteinuria Level

For Proteinuria >1 g/day:

• Start ACE inhibitor or ARB therapy immediately with uptitration as far as tolerated to achieve proteinuria <1 g/day. 1, 2

• Target blood pressure <125/75 mmHg (or <130/80 mmHg per some guidelines) in patients with proteinuria >1 g/day. 2

• Monitor serum creatinine and potassium frequently when initiating or uptitrating ACE inhibitor/ARB therapy. 1

• Do not discontinue ACE inhibitor/ARB if serum creatinine increases up to 30% from baseline, unless kidney function continues to worsen or refractory hyperkalemia develops. 1

For Proteinuria 0.5-1 g/day:

• Consider ACE inhibitor or ARB treatment with target blood pressure <130/80 mmHg. 2

• Implement lifestyle modifications including sodium restriction and weight normalization. 1

For Proteinuria <0.5 g/day:

• Monitor with repeat quantification and focus on cardiovascular risk reduction strategies. 1, 2

Lifestyle Modifications

• Restrict dietary sodium to <2.0 g/day (<90 mmol/day) to reduce proteinuria and improve blood pressure control. 1

• Normalize weight through appropriate diet and exercise to reduce proteinuria. 1

• Counsel patients to hold ACE inhibitor/ARB and diuretics during episodes of volume depletion (illness, diarrhea, vomiting) to prevent acute kidney injury. 1

Nephrology Referral Criteria

With a creatinine of 75 µmol/L (eGFR likely >60 mL/min/1.73 m²), nephrology referral is NOT automatically required based on GFR alone, as the Canadian Society of Nephrology recommends referral for GFR <30 mL/min/1.73 m². 4

However, refer to nephrology if:

• Persistent proteinuria >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol), as renal biopsy may be indicated and immunosuppressive medications may need consideration. 4

• Abrupt sustained decrease in eGFR >20% after excluding reversible causes. 4

• Urinary red cell casts or RBC >20 per high power field sustained and not readily explained. 4

• Hypertension refractory to treatment with 4 or more antihypertensive agents. 4

• Inability to tolerate renal protective medications (ACE inhibitors/ARBs). 4

• Uncertainty about diagnosis or suspected hereditary kidney disease. 4

Monitoring Strategy

• Assess eGFR and proteinuria at least annually in all patients with confirmed proteinuria, with more frequent monitoring for higher-risk patients. 3

• Monitor labs frequently (serum creatinine, potassium, proteinuria levels) when on ACE inhibitor or ARB therapy. 1

Common Pitfalls to Avoid

The vast majority of patients with stage 3 CKD do not progress to ESRD but die mainly from cardiovascular causes, so cardiovascular risk reduction should be strongly emphasized in primary care. 4

Proteinuria <1 g/day can generally be managed in primary care with nonspecific therapy (ACE inhibitors/ARBs, blood pressure control, lifestyle modifications), as kidney biopsy is generally not undertaken when kidney function is stable and proteinuria is <1 g/day. 4

Avoid nephrotoxins including NSAIDs, aminoglycosides, and radiocontrast agents in patients with proteinuria and CKD. 4, 5