Progressive Care Nursing Certification (PCCN) Practice Exam

What does blood urea nitrogen (BUN) reflect?

1. Renal absorption of sodium

2. Liver function

3. Hydration and catabolic state

4. Renal excretion of potassium

The correct answer is: Hydration and catabolic state

Blood urea nitrogen (BUN) primarily reflects hydration status and the catabolic state of the body. BUN is a waste product formed in the liver after proteins are metabolized and is normally excreted by the kidneys. When a patient is dehydrated, the concentration of urea in the blood increases because there's less fluid in the bloodstream to dilute it. Conversely, during a catabolic state—where the body breaks down protein faster than usual, such as in acute illness, trauma, or severe stress—BUN levels can also rise. Therefore, elevated BUN concentrations can indicate either a loss of fluid or increased protein metabolism, providing insights into the patient's overall physiological status. Understanding these aspects allows healthcare professionals to assess renal function indirectly through the BUN levels, but it should not be used in isolation for definitive conclusions about renal function, hydration, or metabolic state. The other options do not accurately represent what BUN measures, as it is not a direct indicator of renal absorption of sodium, liver function, or renal excretion of potassium.