Prerenal azotemia refers to:

• A. A decrease in BUN resulting from severe liver disease
• B. An increase in BUN resulting from dehydration, shock, and/or decreased blood flow to the kidneys
• C. An increase in BUN resulting from severe liver disease
• D. An increase in BUN resulting from the inability to urinate

Answer: (A)

Prerenal azotemia happens when the kidneys aren’t getting enough blood flow, so they conserve urea and BUN rises even though the kidney tissue isn’t damaged. Dehydration, shock, or any condition that reduces renal perfusion leads to a higher BUN, often with a relatively lower rise in creatinine, giving a high BUN:creatinine ratio. This distinguishes prerenal causes from issues arising inside the kidney itself or from urinary obstruction. Liver disease, for example, reduces urea production so BUN may not rise in that context, and inability to urinate points to postrenal (obstructive) causes rather than prerenal.