Elevated blood urea nitrogen (BUN) can be caused by which of the following conditions?

Elevated blood urea nitrogen (BUN) is commonly associated with conditions that lead to decreased renal perfusion or increased protein breakdown. Dehydration and renal dysfunction are particularly relevant because dehydration reduces blood flow to the kidneys, leading to a decreased glomerular filtration rate (GFR). When GFR is compromised, urea, a waste product from protein metabolism, is not efficiently cleared from the bloodstream, resulting in higher BUN levels.

In addition, renal dysfunction can include various types of kidney disease, such as acute kidney injury or chronic renal failure, both of which can lead to elevated BUN as the kidneys lose their ability to filter waste effectively. The combination of these factors makes the situation particularly significant when assessing a patient's renal status and hydration levels.

Conditions like increased hydration typically lead to a dilution of blood constituents, potentially resulting in a lower BUN. Acute glomerulonephritis, while it may result in elevated BUN, is more commonly associated with other findings, such as hematuria or proteinuria, and may not always cause a significant increase in BUN unless coupled with further renal impairment. Hypotension can also affect renal perfusion but is not a direct cause of elevated BUN in the same context as dehydration