Management of Impaired Renal Function (Creatinine 1.8 mg/dL, BUN 37 mg/dL)
Immediately calculate the estimated glomerular filtration rate (eGFR) using the MDRD or CKD-EPI equation to stage kidney disease and guide all subsequent management decisions, as creatinine 1.8 mg/dL represents moderate renal impairment requiring urgent intervention. 1, 2
Immediate Assessment and Risk Stratification
Calculate eGFR immediately using the MDRD equation—this creatinine level (1.5-2.5 mg/dL range) represents mild-to-moderate renal impairment that necessitates action, and serum creatinine alone underestimates severity, particularly in elderly patients with reduced muscle mass 1, 2
Obtain baseline urinalysis and spot urine albumin-to-creatinine ratio to distinguish glomerular from tubular disease and determine prognosis—proteinuria >300 mg/g indicates significant kidney damage and worse outcomes 3, 1, 2
Check serum electrolytes immediately to detect hypokalemia, hypophosphatemia, hypomagnesemia, and metabolic acidosis, as these are common complications requiring correction 3, 1
Perform renal ultrasound urgently if acute kidney injury is suspected to exclude obstructive uropathy, which requires immediate urological intervention 4
Medication Management (Critical Priority)
Discontinue all NSAIDs immediately—these are absolutely contraindicated with creatinine >1.5 mg/dL and represent a common reversible cause of renal dysfunction 1, 2
Stop all nephrotoxic medications including aminoglycosides, contrast agents, and herbal supplements without delay 1, 4
Adjust doses of all renally-cleared medications when eGFR <60 mL/min/1.73 m² according to package inserts—failure to do so increases toxicity risk 3, 2
Review ACE inhibitors and ARBs carefully—if the patient is on these agents, monitor closely for hyperkalemia and further creatinine elevation, but do not automatically discontinue if creatinine increases up to 30% from baseline, as this represents expected hemodynamic changes 2, 5, 6
Avoid iodinated contrast media for imaging studies—if angiography is absolutely required, use isosmolar contrast agents and ensure adequate hydration, as contrast-induced nephropathy risk is significantly elevated with baseline renal impairment 2, 7
Blood Pressure and Cardiovascular Management
Target blood pressure ≤140/90 mmHg if proteinuria <30 mg/24 hours, or ≤130/80 mmHg if proteinuria ≥30 mg/24 hours to slow progression of kidney disease 2
Initiate ACE inhibitor or ARB as first-line therapy if proteinuria >300 mg/24 hours and uptitrate to maximally tolerated doses, monitoring creatinine and potassium within 7-14 days after initiation 2, 5, 6
Do not discontinue ACE inhibitor/ARB if serum creatinine increases up to 30% from baseline—this is expected and acceptable, representing hemodynamic changes rather than progressive kidney damage 2
Monitor serum potassium periodically as ACE inhibitors and ARBs can cause hyperkalemia, particularly with eGFR <60 mL/min/1.73 m² 5, 6
Dietary and Lifestyle Modifications
Restrict dietary sodium to <2 g/day to control blood pressure and reduce proteinuria 1, 2
Target BMI 20-25 kg/m² through weight management if overweight or obese 2
Counsel complete smoking cessation and encourage regular exercise as part of cardiovascular risk modification 2
If eGFR <30 mL/min/1.73 m², restrict protein intake to 0.6-0.8 g/kg/day to slow progression 1
Monitoring Strategy
Recheck serum creatinine, eGFR, electrolytes, and proteinuria within 7-14 days after any medication adjustments or initiation of renoprotective therapy 1
Monitor every 3-4 months once stable, including serum creatinine, eGFR, electrolytes, proteinuria, and blood pressure 2
Define disease progression as a change in GFR category plus ≥25% decline in eGFR from baseline—if this occurs, increase monitoring frequency and intensify treatment 2
Screen for CKD complications including anemia, metabolic bone disease, and metabolic acidosis, as these become prevalent when eGFR <60 mL/min/1.73 m² 2
When to Refer to Nephrology
Refer to nephrology if creatinine remains elevated despite 4 weeks of conservative management or if there is persistent proteinuria grade ≥1+ by dipstick analysis 3, 1
Urgent nephrology consultation is required if creatinine ≥3× baseline, absolute value ≥4.0 mg/dL, or rapidly declining kidney function (>25% eGFR loss in 3 months) 1, 4
Refer if active urinary sediment is present suggesting glomerulonephritis, as this requires subspecialty evaluation and possible kidney biopsy 1, 4
Critical Pitfalls to Avoid
Do not rely solely on serum creatinine to assess renal function—it has poor sensitivity for detecting renal dysfunction, and up to 46% of patients with normal serum creatinine have measured creatinine clearance <60 mL/min 2, 8
Do not assume stable renal function means no progression—21% of patients with mild renal dysfunction at baseline develop severe renal dysfunction during follow-up, particularly those with heart failure or higher CHADS2 scores 8
Be aware that certain medications elevate serum creatinine without affecting renal function—cobicistat, dolutegravir, and trimethoprim affect creatinine secretion, creating falsely elevated values 3
Recognize that patients at this level of renal impairment have lost renal reserve and are at increased risk for acute kidney injury from any additional insult, requiring heightened vigilance 2