From the Guidelines
Elevated blood urea nitrogen (BUN) is a significant indicator of potential kidney dysfunction or dehydration, and levels above 20 mg/dL, as seen in 1, can be particularly concerning, warranting prompt medical evaluation. The implications of elevated BUN are multifaceted, involving potential kidney issues, dehydration, or other underlying health problems. Normal BUN ranges from 7-20 mg/dL, with higher levels suggesting impaired kidney function in filtering waste products. Common causes include:
- Dehydration
- High-protein diet
- Gastrointestinal bleeding
- Heart failure
- Kidney disease
- Certain medications like NSAIDs and diuretics Given the potential severity of elevated BUN, especially at levels above 20 mg/dL as indicated in 1, it is crucial to:
- Increase fluid intake to 2-3 liters daily unless contraindicated
- Temporarily reduce protein consumption
- Consult a healthcare provider promptly for further evaluation and guidance The healthcare provider may recommend:
- Discontinuing problematic medications
- Ordering additional tests like creatinine levels or a complete metabolic panel
- Referring to a nephrologist if kidney disease is suspected The BUN-to-creatinine ratio is a valuable tool in differentiating between pre-renal causes, such as dehydration, and intrinsic kidney problems, guiding appropriate treatment. Elevated BUN levels, as discussed in 1 and 1, underscore the importance of monitoring and addressing kidney function to prevent further complications.
From the Research
Implications of Elevated Blood Urea Nitrogen (BUN)
Elevated Blood Urea Nitrogen (BUN) has several implications, including:
- Increased risk of mortality: A study found that an elevated BUN was associated with a nearly 2-fold increased risk of mortality in older, medically stable Veterans 2.
- Indicator of global health status: Elevated BUN may be reflective of global health status rather than solely an indicator of the severity of acute illness or unstable chronic disease 2.
- Diagnostic tool for acute kidney injury (AKI): BUN and serum creatinine are commonly used to diagnose AKI, but they are not very sensitive or specific for the diagnosis of AKI 3.
- Predictor of long-term kidney outcomes: Biomarkers of AKI, including BUN, may predict long-term kidney outcomes and mortality 3.
- Association with hospital mortality: A study found that patients with a high BUN/creatinine ratio had higher hospital mortality compared to those with a low BUN/creatinine ratio 4.
Clinical Applications
Elevated BUN has several clinical applications, including:
- Differentiating the site of gastrointestinal bleeding: The BUN/creatinine ratio can be used to differentiate between upper and lower gastrointestinal bleeding 5.
- Assessing prognosis in patients with acute nonvariceal upper gastrointestinal bleeding (ANVUGIB): The early dynamic elevated BUN/creatinine ratio after admission can be used to predict clinical outcomes in patients with ANVUGIB 5.
- Monitoring kidney function: BUN and serum creatinine are commonly used to monitor kidney function in patients with AKI or chronic kidney disease 6.