From the Guidelines
A BUN of 28 mg/dL and a creatinine of 1.04 mg/dL are not specifically indicative of an acute kidney injury (AKI). These values show a mildly elevated BUN with a normal creatinine level, according to the most recent guidelines on renal failure 1. The BUN/creatinine ratio is approximately 27:1, which is somewhat elevated compared to the normal ratio of 10-20:1. This pattern can occur in various conditions including mild dehydration, high protein diet, gastrointestinal bleeding, or certain medications, rather than necessarily indicating kidney damage.
To properly assess kidney function, these values should be compared to the patient's baseline levels, as an acute increase from baseline would be more concerning for AKI, as defined by an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline 1. Additional clinical information such as urine output, other laboratory values, and the patient's overall condition are essential for a complete assessment of kidney function.
Some studies suggest that BUN can be a better predictor of outcome than creatinine or estimated GFR in certain conditions, such as acute heart failure 1. However, in the context of AKI, the most recent and highest quality study prioritizes the measurement of serum creatinine and urine output for diagnosis 1. If there is concern about kidney function, monitoring these values over time and consulting with a healthcare provider for a comprehensive evaluation would be appropriate, taking into account the patient's individual clinical context and baseline values.
From the Research
Blood Urea Nitrogen (BUN) and Creatinine Levels
- A BUN level of 28 mg/dL and a creatinine level of 1.04 mg/dL can be evaluated in the context of renal function, as discussed in 2 and 3.
- Normal BUN levels are typically considered to be between 10-20 mg/100 mL, and normal creatinine levels are between 0.6-1.2 mg/100 mL, as stated in 3.
- The BUN to creatinine ratio can also be useful in interpreting these values, with a ratio of greater than 25:1 suggesting an extrarenal problem, and a ratio of 10:1 suggesting renal failure, as noted in 3.
Comparison to Normal Ranges
- The normal ranges for BUN and creatinine can vary depending on the laboratory and the individual's age, as discussed in 4.
- In elderly subjects, the normal range for BUN is estimated to be 14-23 mg/dL, and for creatinine, it is 0.9-1.3 mg/dL for males and 0.7-1.1 mg/dL for females, as found in 4.
- The provided BUN and creatinine levels can be compared to these normal ranges to determine if they are within the expected range.
Diagnostic Values
- BUN and creatinine levels can be used as diagnostic tools to distinguish between different conditions, such as heart failure, asthma, and chronic obstructive pulmonary disease, as discussed in 5.
- The cutoff values for BUN and creatinine can be used to differentiate between these conditions, with a BUN level of 20.45 mg/dL and a creatinine level of 0.782 mg/dL being potential biomarkers, as found in 5.
- The role of BUN and creatinine in prognostic assessment of chronic heart failure is also highlighted in 6, where optimal cut-off values were determined using ROC analysis.