The blood urea nitrogen (BUN) to creatinine ratio is a valuable diagnostic tool used to assess kidney function and hydration status. It is determined by dividing the BUN value (measured in mg/dL) by the creatinine value (measured in mg/dL). For example, if a patient’s BUN is 20 mg/dL and their creatinine is 1 mg/dL, the ratio is 20:1.
This ratio is important because it provides insights beyond what BUN and creatinine levels alone can offer. Elevated ratios may indicate dehydration, increased protein catabolism, or decreased renal perfusion. Conversely, decreased ratios may suggest liver disease, malnutrition, or certain instances of acute tubular necrosis. The ratio’s historical context is rooted in the development of clinical chemistry and the understanding of renal physiology.