How to diagnose and manage a patient with impaired renal function, elevated Creatinine (Cr), and elevated Blood Urea Nitrogen (BUN)?

From the Guidelines

Diagnosing and managing a patient with impaired renal function, such as a patient with a GFR of 50, Cr of 1.6, and BUN of 30, requires a comprehensive approach that prioritizes the calculation of the estimated glomerular filtration rate (eGFR) using the CKD-EPI or MDRD equation, as recommended by the most recent guidelines 1.

Key Steps in Diagnosis

• Confirm kidney dysfunction through repeat laboratory testing of creatinine and BUN
• Calculate the eGFR using the CKD-EPI or MDRD equation to determine the stage of chronic kidney disease (CKD)
• Obtain a complete history focusing on potential nephrotoxic exposures, medications, and comorbidities like diabetes or hypertension
• Perform a thorough physical examination assessing volume status, blood pressure, and signs of systemic diseases
• Order a urinalysis to evaluate for proteinuria, hematuria, or casts, and obtain a renal ultrasound to assess kidney size, structure, and rule out obstruction

Management Strategies

• Address reversible causes such as discontinuing nephrotoxic medications and treating dehydration
• Adjust medication dosages based on kidney function, particularly for renally cleared drugs
• Control blood pressure to target levels below 130/80 mmHg using ACE inhibitors or ARBs if proteinuria is present, as supported by recent studies 1
• Manage diabetes with a target HbA1c of 7-8% using kidney-friendly medications like SGLT2 inhibitors
• Implement dietary modifications including sodium restriction to 2-3g daily and protein limitation to 0.8g/kg/day
• Monitor kidney function regularly, with frequency based on CKD stage, and consider nephrology referral for severe kidney dysfunction (eGFR <30 ml/min), rapid decline in function, significant proteinuria, or complex cases requiring specialized management, as outlined in guidelines from the National Kidney Foundation 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Diagnosing Chronic Kidney Disease (CKD)

To diagnose CKD, the following criteria should be considered:

• A persistent abnormality in kidney structure or function, such as a glomerular filtration rate (GFR) <60 mL/min/1.73 m2 or albuminuria ≥30 mg per 24 hours, for more than 3 months 2
• Elevated Creatinine (Cr) and Blood Urea Nitrogen (BUN) levels, such as Cr 1.6 and BUN 30, may indicate impaired renal function

Diagnostic Evaluation

The diagnostic evaluation of CKD should include:

• History and physical examination to identify potential causes of CKD, such as diabetes and hypertension
• Urinalysis to detect albuminuria or other abnormalities in the urine
• Imaging studies, such as ultrasound or CT scans, to evaluate kidney structure and function 3
• Calculation of GFR using a formula, such as the Modification of Diet in Renal Disease (MDRD) study equation or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation

Management of CKD

The management of CKD should include:

• Cardiovascular risk reduction, such as statins and blood pressure management
• Treatment of albuminuria, such as angiotensin-converting enzyme inhibitors (ACEis) or angiotensin II receptor blockers (ARBs)
• Avoidance of potential nephrotoxins, such as nonsteroidal anti-inflammatory drugs (NSAIDs)
• Adjustments to drug dosing, such as many antibiotics and oral hypoglycemic agents 2
• Monitoring for complications of CKD, such as hyperkalemia, metabolic acidosis, hyperphosphatemia, vitamin D deficiency, secondary hyperparathyroidism, and anemia

Use of ACEis or ARBs in CKD

The use of ACEis or ARBs in CKD has been shown to be effective in reducing the risk of kidney failure and death:

• A systematic review and meta-analysis of clinical trials found that ACEi or ARB treatment initiation led to a lower risk of kidney failure with replacement therapy (KFRT) in patients with advanced CKD 4
• Trends in ACEi and ARB use among those with impaired kidney function in the United States have been increasing over time, but there is still a significant gap in preventive care delivery for adults with hypertension and albuminuria 5, 6