BUN 28 mg/dL with creatinine 1.0 mg/dL. What does the BUN/Cr ratio suggest?

BUN 28 mg/dL with creatinine 1.0 mg/dL. What does the BUN/Cr ratio suggest?

• A. Approximately 28:1, suggesting prerenal azotemia
• B. Approximately 10:1, suggesting prerenal azotemia
• C. Approximately 50:1, dehydration
• D. Approximately 2:1, intrarenal injury

Answer: (A)

The BUN/creatinine ratio helps distinguish prerenal azotemia (reduced kidney perfusion) from intrinsic kidney injury. When perfusion is decreased, the kidney reabsorbs more urea, so BUN rises disproportionately to creatinine, which stays more constant as the glomerular filtration rate is affected. Here, BUN is 28 mg/dL and creatinine is 1.0 mg/dL, giving a ratio of about 28:1. That elevated ratio points toward prerenal azotemia, often seen with dehydration or volume depletion. In intrinsic renal injury, the ratio tends to be lower (roughly 10–15:1) because creatinine rises more in proportion to BUN. A very high ratio like 50:1 isn’t supported by these values, and a very low ratio like 2:1 would not fit prerenal processes. So the best interpretation is prerenal azotemia due to reduced renal perfusion.

The BUN/creatinine ratio helps distinguish prerenal azotemia (reduced kidney perfusion) from intrinsic kidney injury. When perfusion is decreased, the kidney reabsorbs more urea, so BUN rises disproportionately to creatinine, which stays more constant as the glomerular filtration rate is affected. Here, BUN is 28 mg/dL and creatinine is 1.0 mg/dL, giving a ratio of about 28:1. That elevated ratio points toward prerenal azotemia, often seen with dehydration or volume depletion. In intrinsic renal injury, the ratio tends to be lower (roughly 10–15:1) because creatinine rises more in proportion to BUN. A very high ratio like 50:1 isn’t supported by these values, and a very low ratio like 2:1 would not fit prerenal processes. So the best interpretation is prerenal azotemia due to reduced renal perfusion.