Final answer:
An elevated blood urea nitrogen (BUN) level with a normal creatinine level often indicates pre-renal causes, such as dehydration or heart failure, influencing kidney function, but not directly related to the kidney's ability to filter waste. Further tests are needed to identify the exact cause.
Step-by-step explanation:
If the blood urea nitrogen (BUN) is elevated but the creatinine is normal, it suggests that there may be a condition affecting kidney function where the problem is not directly related to the kidney's filtration capability. The BUN level is an estimate of urea in the blood and is an indicator of kidney function. Several conditions may cause an elevated BUN while creatinine levels remain normal, including pre-renal causes such as dehydration or heart failure, where less blood reaches the kidneys.
An elevated BUN with normal creatinine could also be related to non-renal issues such as gastrointestinal bleeding or increased protein in the diet. However, it's important to consider other factors and conduct further testing to understand the cause of the high BUN level. In contrast, the glomerular filtration rate (GFR), which can be measured indirectly by the creatinine clearance test, is not indicated here as abnormal, since creatinine levels are within the normal range.