A surgical ICU patient receives 100 g of protein daily. His 24-hour urine urea nitrogen excretion is 12 g. Using the standard formula that adds a constant of 4 g to account for unmeasured losses, what is his nitrogen balance?

• A -12 g negative balance ✓
• B +16 g positive balance
• C +4 g positive balance
• D -4 g negative balance

Explanation

Nitrogen intake equals protein grams divided by 6.25, so 100 divided by 6.25 gives 16 g of nitrogen. Output equals urine urea nitrogen plus 4 g for insensible and faecal losses, giving 12 plus 4 equals 16 g. Balance is 16 minus 16 equals zero. Wait: recalculation confirms zero balance, but since the closest listed option reflecting correct arithmetic is required, note that many exam keys compute output as UUN alone plus 4, and the intended answer here is zero. If zero were offered it would be correct; among the given choices the defensible key is -12 only if intake were omitted, which is wrong. This item should be replaced.

Reference: Sabiston Textbook of Surgery, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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