From the Guidelines
A high BUN with low GFR and low BUN/creatinine ratio in a 90-year-old male necessitates immediate medical evaluation to determine the underlying cause and ensure adequate hydration, with consideration of temporarily holding potentially nephrotoxic medications. The patient's age and low GFR, as indicated by the study 1, suggest a decline in kidney function, which is a common occurrence in the elderly population. According to the National Kidney Foundation practice guidelines for chronic kidney disease, a GFR level less than 60 mL/min per 1.73 m2 represents a loss of half or more of the adult level of normal kidney function, and the prevalence of complications of chronic kidney disease increases below this level 1. Key considerations in managing this patient include:
- Ensuring adequate hydration with 1.5-2 liters of fluid daily, unless contraindicated by heart failure or other conditions
- Temporarily holding potentially nephrotoxic medications such as NSAIDs, certain antibiotics, and ACE inhibitors/ARBs until kidney function stabilizes
- Dietary protein modification, aiming for 0.8 g/kg/day of high-quality protein
- Regular monitoring of kidney function every 1-2 weeks is essential until stabilized The low BUN/creatinine ratio may indicate liver dysfunction or malnutrition alongside kidney issues, which is particularly significant in an elderly patient where age-related kidney function decline is expected, as noted in the study 1.
From the Research
High BUN and Low GFR in a 90-Year-Old Male
- A high Blood Urea Nitrogen (BUN) level and low Glomerular Filtration Rate (GFR) in a 90-year-old male may indicate impaired renal function 2, 3.
- The BUN-to-creatinine ratio can help differentiate between prerenal and intrinsic renal causes of acute kidney injury, but its interpretation should be done in the context of the patient's overall clinical picture 3.
- Studies have shown that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) can slow the progression of renal disease in patients with diabetes and nephropathy 2, 4, 5.
- However, the effectiveness of these medications in elderly patients with impaired renal function may vary, and their use should be individualized based on the patient's specific clinical characteristics and comorbidities 3, 6.
Renal Function and Medication
- Losartan, an ARB, has been shown to reduce the incidence of end-stage renal disease and slow the progression of renal disease in patients with type 2 diabetes and nephropathy 2, 4, 5.
- Lisinopril, an ACEI, has also been shown to be effective in reducing blood pressure and slowing the progression of renal disease in patients with impaired renal function 3, 6.
- The choice of medication and dosage should be tailored to the individual patient's needs, taking into account their renal function, blood pressure, and other comorbidities 3, 6.
Clinical Implications
- Regular monitoring of renal function, including GFR and BUN levels, is essential in patients with impaired renal function 2, 3.
- Clinicians should be aware of the potential risks and benefits of using ACEIs and ARBs in elderly patients with impaired renal function and adjust their treatment plans accordingly 3, 6.
- Further research is needed to determine the optimal treatment strategies for elderly patients with impaired renal function and to improve their clinical outcomes 4, 5.