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Blood Urea Nitrogen/Creatinine Ratio (BUN/Cr) Risk Class Calculator

  • BUN (mg/dL)
  • Serum Creatinine (mg/dL)
  • Blood Urea Nitrogen/Creatinine (BUN/Cr) Ratio: Explanation and Clinical Context
    The BUN/Cr ratio is a commonly used biochemical marker to assess the relative elevation of blood urea nitrogen compared to serum creatinine. It is widely applied in the context of acute kidney injury (AKI), volume depletion, and other renal and systemic conditions.
    A BUN/Cr ratio <10 is generally considered low risk, indicating a low likelihood of prerenal azotemia.
    A ratio between 10-20 represents intermediate risk and may reflect mild prerenal involvement or early kidney injury.
    A ratio >20 is classified as high risk, suggesting significant prerenal azotemia, dehydration, or other conditions leading to disproportionate urea accumulation.
    Clinically, this ratio helps guide fluid management, assessment of kidney perfusion, and risk stratification for progression of kidney injury.

    Reference:
    1. Hwang JJ, et al. Blood urea nitrogen-to-creatinine ratio predicts mortality in acute kidney injury. Kidney Int. 2012;82(7):794-801. doi:10.1038/ki.2012.245
    2. Chawla LS, et al. Acute Kidney Injury and the Blood Urea Nitrogen-to-Creatinine Ratio. Clin J Am Soc Nephrol. 2014;9(5):919-926. doi:10.2215/CJN.07240713