When estimating nitrogen balance from urinary urea nitrogen, which statement best describes the underlying assumption and a more reliable alternative?

• A. Urinary urea nitrogen accounts for about 80% of total urinary nitrogen losses; a more reliable measure is total urinary nitrogen.
• B. Urinary urea nitrogen accounts for about 60%; a more reliable measure is serum albumin.
• C. Urinary urea nitrogen accounts for about 70%; stress has no effect.
• D. Urinary urea nitrogen accounts for about 90%; a more reliable measure is urinary creatinine.

Answer: (A)