In suspected renal disease, urinalysis helps interpret BUN and creatinine via which parameter?

• A. Urine pH
• B. Urine electrolytes
• C. Urine Specific Gravity
• D. Urine protein concentration

Answer: (C)

Urine specific gravity is the parameter that best helps interpret BUN and creatinine in suspected renal disease because it shows the kidney’s ability to concentrate urine, which reflects both hydration status and tubular function. When dehydration or another prerenal factor lowers blood flow to the kidneys, the kidneys conserve water and the urine becomes concentrated (high SG). This tends to raise BUN relative to creatinine, helping explain an azotemia that is prerenal in origin. If the kidney itself is damaged and can’t concentrate urine well, the urine is dilute (low SG or isosthenic), which changes the BUN/creatinine relationship and points toward intrinsic renal disease. Other urinalysis measures like pH, electrolytes, or protein concentration provide useful information, but none relate as directly to interpreting BUN and creatinine as the ability of the kidneys to concentrate urine.