In suspected prerenal AKI, how is the BUN/creatinine ratio interpreted?

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Multiple Choice

In suspected prerenal AKI, how is the BUN/creatinine ratio interpreted?

When perfusion to the kidneys drops, the body conserves water by reabsorbing more solutes, including urea. Urea is reabsorbed to a greater extent than creatinine in this prerenal state, so BUN rises disproportionately while creatinine stays relatively less elevated. That pattern yields a BUN/creatinine ratio greater than about 20:1, with creatinine relatively preserved. This helps distinguish prerenal azotemia from intrinsic renal injury, where the ratio is often lower because urea reabsorption isn’t as pronounced and creatinine rises more. Keep in mind factors like high protein intake or GI bleeding can also raise BUN and affect the ratio.

When perfusion to the kidneys drops, the body conserves water by reabsorbing more solutes, including urea. Urea is reabsorbed to a greater extent than creatinine in this prerenal state, so BUN rises disproportionately while creatinine stays relatively less elevated. That pattern yields a BUN/creatinine ratio greater than about 20:1, with creatinine relatively preserved. This helps distinguish prerenal azotemia from intrinsic renal injury, where the ratio is often lower because urea reabsorption isn’t as pronounced and creatinine rises more. Keep in mind factors like high protein intake or GI bleeding can also raise BUN and affect the ratio.

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