Elevated BUN most often indicates which organ system issue?

• A. Hepatic failure
• B. Pulmonary disease
• C. Renal disease
• D. Endocrine disorders

Answer: (C)

BUN elevation points to the kidneys’ ability to filter waste from the blood. Urea is produced in the liver from ammonia and is normally cleared by the kidneys into urine. When renal function is impaired—due to acute injury, chronic disease, or reduced renal perfusion—the kidneys can’t excrete urea effectively, so its level rises in the blood. While factors like hydration and protein intake can influence BUN, a rise most consistently reflects renal trouble. In contrast, liver disease tends to lower BUN since production of urea is reduced, and pulmonary or endocrine disorders don’t directly cause a rise in BUN as a primary finding.