From the Guidelines
The renal function assessment indicates moderate kidney impairment, suggesting Stage 3a Chronic Kidney Disease, and I recommend consulting with a nephrologist for comprehensive evaluation and management. The elevated BUN (Blood Urea Nitrogen) of 41 mg/dL, slightly elevated creatinine of 1.1 mg/dL, and reduced GFR (Glomerular Filtration Rate) of 47 mL/min/1.73m² are consistent with this diagnosis, as defined by the National Kidney Foundation practice guidelines for chronic kidney disease: evaluation, classification, and stratification 1.
According to the guidelines, chronic kidney disease is defined as either kidney damage or decreased kidney function (decreased GFR) for 3 or more months, and the GFR level less than 60 mL/min per 1.73 m2 represents loss of half or more of the adult level of normal kidney function 1.
Medication dosages for renally-cleared drugs should be adjusted accordingly, and nephrotoxic medications should be avoided when possible, as recommended by the Kidney Disease: Improving Global Outcomes 2012 clinical practice guideline 1. Regular monitoring of renal function every 3-6 months is advised, along with blood pressure control, preferably with an ACE inhibitor or ARB if not contraindicated.
Dietary modifications including sodium restriction (less than 2g daily), moderate protein intake (0.8g/kg/day), and potassium restriction may be necessary depending on additional lab values. The elevated BUN-to-creatinine ratio (>20:1) suggests possible pre-renal causes such as dehydration, heart failure, or excessive protein intake, which should be investigated, as discussed in the acr appropriateness criteria® renal failure study 1.
This level of kidney function requires attention but is not immediately life-threatening; however, progression should be prevented through careful management of underlying conditions like diabetes or hypertension, as emphasized in the national kidney foundation practice guidelines for chronic kidney disease: evaluation, classification, and stratification 1.
Key recommendations for management include:
- Consulting with a nephrologist for comprehensive evaluation and management
- Adjusting medication dosages for renally-cleared drugs and avoiding nephrotoxic medications
- Regular monitoring of renal function every 3-6 months
- Blood pressure control with an ACE inhibitor or ARB if not contraindicated
- Dietary modifications as necessary
- Investigating possible pre-renal causes of the elevated BUN-to-creatinine ratio.
From the FDA Drug Label
Impaired renal function decreases elimination of lisinopril, which is excreted principally through the kidneys, but this decrease becomes clinically important only when the glomerular filtration rate is below 30 mL/min. Above this glomerular filtration rate, the elimination half-life is little changed
- The patient's GFR is 47, which is above 30 mL/min.
- The decrease in elimination of lisinopril due to impaired renal function is not clinically important at this GFR level.
- No dose adjustment is necessary based on the information provided in the drug label 2.
From the Research
Assessment of Renal Function
The patient's renal function can be assessed based on the provided laboratory values: BUN 41, Cr 1.1, and GFR 47.
- The GFR value of 47 mL/min/1.73 m2 indicates impaired renal function, as a normal GFR is typically above 60 mL/min/1.73 m2 3.
- The BUN and creatinine levels are also elevated, which can be indicative of renal dysfunction.
Chronic Kidney Disease (CKD) Diagnosis and Management
According to the study by 3, CKD is defined as a persistent abnormality in kidney structure or function, such as a GFR <60 mL/min/1.73 m2, for more than 3 months.
- The patient's GFR value of 47 mL/min/1.73 m2 suggests that they may have CKD.
- The study also highlights the importance of optimal management of CKD, including cardiovascular risk reduction, treatment of albuminuria, and avoidance of potential nephrotoxins.
ACE Inhibitors and ARBs in CKD
The use of ACE inhibitors and ARBs in patients with CKD is supported by several studies:
- A study by 4 found that the use of ACE inhibitors and ARBs in patients with heart failure and CKD did not worsen renal function and may even have beneficial effects.
- Another study by 5 suggested that ACE inhibitors and ARBs can slow the progression of renal insufficiency in patients with proteinuric kidney disease.
- However, a study by 6 found that discontinuation of ACE inhibitors and ARBs was common in patients with CKD, particularly in those with more advanced disease.
- A review article by 7 provides guidance on managing the adverse effects of ACE inhibitors and ARBs, including declining renal function and hyperkalemia.