A nurse is caring for a male client who reports nausea and vomiting and is receiving IV fluid therapy. His blood urea nitrogen (BUN) is 32 mg/dL (Range 8-24 mg/dl), creatinine 1.1 mg/dL (Range 0.7-1.3 mg/dl), and hematocrit 50% (range 40-54%). Which of the following nursing interventions is appropriate?

A. The BUN is elevated (32 mg/dL), although creatinine is normal, suggesting possible dehydration, not routine results. B. Decreasing fluids would worsen dehydration and is inappropriate. C. There's no indication of infection such as fever or foul-smelling urine, so a urine culture is not the priority. D. Evaluating urine output and specific gravity helps determine hydration status and renal perfusion. High BUN with normal creatinine and elevated hematocrit may indicate hemoconcentration due to fluid volume deficit, so urine assessment is a logical next step.