What does a BUN creatinine ratio greater than 20 indicate?

A BUN (blood urea nitrogen) to creatinine ratio greater than 20 typically indicates pre-renal problems. This condition often arises from factors that affect blood flow to the kidneys, such as dehydration or heart failure. In a pre-renal scenario, the kidneys are responding to a perceived lack of perfusion, leading to increased reabsorption of urea and a relatively higher BUN compared to creatinine. This is crucial for understanding how the kidneys respond to different conditions.

While a BUN to creatinine ratio can provide insightful diagnostic clues, a ratio above 20 is specifically tied to these pre-renal causes, often reflecting the state of hydration or blood volume in the patient. It's important in clinical contexts to distinguish among the types of renal dysfunction to determine the underlying issue accurately. Thus, a high ratio is indicative of processes that dilute creatinine while urea reabsorption remains relatively high, typically associated with hypoperfusion of the kidneys rather than intrinsic renal damage.