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urea nitrogen (BUN)/creatinine ratio
The ratio to serum urea nitrogen to serum creatinine used to assess hydration status.
Clinical significance:
- a value of > 20 suggests prerenal azotemia
Notes:
- Acute or chronic renal failure is the most common cause of high BUN levels.
- In prerenal failure, a low renal blood supply, such as occurs with hypovolemia or congestive heart failure, leads to reduced glomerular filtration & therefore an elevated BUN.
- In renal failure, damage to the nephrons, particularly such as occurs with glomerulonephritis or pyelonephritis, leads to decreased glomerular filtration & excretion.
- Blood urea nitrogen begins to rise when the glomerular filtration rate (GFR) falls below 50 mL/min due to increased resorption of urea in the proximal tubules (the normal GFR in an average size manis approximately 125 mL/min).
- The BUN/creatinine ratio increases as well (> 20).
General
urine creatinine ratio
References
- Medical Knowledge Self Assessment Program (MKSAP) 19
Board Basics. An Enhancement to MKSAP19.
American College of Physicians, Philadelphia 2022