What does an increase in BUN likely indicate?

An increase in Blood Urea Nitrogen (BUN) typically indicates a potential issue with kidney function, which aligns with the notion of kidney failure. BUN is a waste product formed in the liver from the breakdown of protein and is normally filtered out of the blood by the kidneys. When the kidneys are not functioning properly, they are less effective at removing BUN from the bloodstream, leading to elevated levels.

While dehydration can also result in increased BUN levels, it is primarily due to reduced fluid volume that concentrates the BUN in the body rather than an actual failure of the kidney's filtering capability. Likewise, conditions like liver disease can influence BUN production but typically lead to normal levels unless there is concurrent renal impairment. Heart failure may lead to increased BUN due to reduced renal blood flow but is not the primary cause. In contrast, kidney failure directly impairs the removal of BUN, making it the most accurate interpretation of elevated levels.