From the Guidelines
Impaired renal function is primarily identified through laboratory tests including elevated serum creatinine, decreased glomerular filtration rate (GFR), abnormal urinalysis showing proteinuria or hematuria, and elevated blood urea nitrogen (BUN), with management strategies focusing on treating underlying causes and controlling blood pressure using ACE inhibitors or ARBs, as recommended by the most recent guidelines 1. Key indicators of impaired renal function include:
- Elevated serum creatinine
- Decreased GFR
- Abnormal urinalysis showing proteinuria or hematuria
- Elevated blood urea nitrogen (BUN) Management strategies should prioritize:
- Treating underlying causes
- Controlling blood pressure (target <130/80 mmHg) using ACE inhibitors like enalapril (5-40 mg daily) or ARBs such as losartan (25-100 mg daily) 1
- Dietary modifications, including sodium restriction (<2g/day), protein moderation (0.8g/kg/day for moderate impairment, 0.6g/kg/day for severe cases), and potassium restriction in advanced disease
- Glycemic control is critical for diabetic patients, targeting HbA1c <7% 1
- Avoiding nephrotoxic medications, including NSAIDs, certain antibiotics like aminoglycosides, and contrast agents when possible
- Regular monitoring of renal function, electrolytes, and proteinuria is necessary, with frequency based on disease severity, as outlined in the guidelines 1 The most recent guidelines emphasize the importance of team-based care, comprehensive medication management, and effective transitions of care to improve outcomes for patients with impaired renal function 1.
From the FDA Drug Label
In patients with severe congestive heart failure whose renal function may depend on the activity of the renin-angiotensin-aldosterone system, treatment with ACE inhibitors, including ramipril, may be associated with oliguria or progressive azotemia and rarely with acute renal failure or death In hypertensive patients with unilateral or bilateral renal artery stenosis, increases in blood urea nitrogen and serum creatinine may occur. A single-dose pharmacokinetic study was conducted in hypertensive patients with varying degrees of renal impairment who received a single 10 mg dose of ramipril. Patients were stratified into four groups based on initial estimates of creatinine clearance: normal (>80 mL/min), mild impairment (40-80 mL/min), moderate impairment (15-40 mL/min), and severe impairment (<15 mL/min).
The key indicators of impaired renal (kidney) function on blood test results include:
- Blood Urea Nitrogen (BUN): increased levels
- Serum Creatinine: increased levels
- Creatinine Clearance: decreased levels, with normal being >80 mL/min, mild impairment being 40-80 mL/min, moderate impairment being 15-40 mL/min, and severe impairment being <15 mL/min
- eGFR (estimated Glomerular Filtration Rate): decreased levels, with normal being >60 mL/min/1.73 m^2
Management strategies for impaired renal function include:
- Monitoring renal function: regularly checking BUN, serum creatinine, and creatinine clearance levels
- Adjusting medication: reducing the dose of ramipril or discontinuing diuretic therapy
- Avoiding nephrotoxic agents: avoiding the use of contrast agents or other medications that may worsen renal function
- Maintaining adequate hydration: ensuring patients are well-hydrated to prevent dehydration and worsening renal function 2, 2
From the Research
Key Indicators of Kidney Function
- Glomerular filtration rate (GFR) is the best indicator of kidney function 3
- Serum creatinine (SCr) and serum cystatin C (SCysC) are commonly used biomarkers to evaluate renal function 4
- GFR can be estimated using equations such as the creatinine-based Cockcroft-Gault and the modification of diet in renal disease 3
- The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation demonstrates higher accuracy of patient classification in earlier stages of disease 3
Management Strategies for Impaired Renal Function
- Estimating GFR using SCr and SCysC can help identify patients with chronic kidney disease (CKD) 4
- Measured GFR or creatinine clearance may be helpful in high-risk patients with normal SCr levels 5
- GFR estimating equations should be reserved for patients with identified CKD 5
- Direct measurement of GFR using an exogenous marker such as iohexol may be necessary in certain clinical scenarios, such as extreme body composition or disagreement between creatinine- and cystatin C-based estimated GFR 6
- Albuminuria assessment, including measuring urine albumin and creatinine in an untimed spot urine collection, can help detect and stage acute and chronic kidney diseases 7
Clinical Indications for Measured GFR
- Measured GFR may be necessary in patients with extreme body composition, Black race, or disagreement between creatinine- and cystatin C-based estimated GFR 6
- Measured GFR may be necessary in patients with liver cirrhosis, advanced chronic kidney disease, or those transitioning to kidney replacement therapy 6
- Measured GFR may be necessary in non-kidney solid organ transplant recipients and living kidney donors 6