The nurse reviews the kidney function blood studies of four clients. Which client's results indicate kidney impairment?

• A. Client 1: Serum Creatinine 0.1 mg/dL; BUN 16 mg/dL
• B. Client 2: Serum Creatinine 0.8 mg/dL; BUN 18 mg/dL
• C. Client 3: Serum Creatinine 1.2 mg/dL; BUN 20 mg/dL
• D. Client 4: Serum Creatinine 1.9; BUN 22 mg/dL

Answer: (D)

Elevated serum creatinine is the clearest sign of reduced kidney filtration. Creatinine is produced at a nearly constant rate and is normally cleared by the kidneys; when glomerular filtration drops, creatinine accumulates in the blood. BUN can rise for several non-kidney reasons (dehydration, high protein intake, catabolic states), so it’s a less specific marker.

In these values, the first three clients have creatinine levels within or near the normal range, while the fourth client has a markedly elevated creatinine of 1.9 mg/dL with a modestly increased BUN of 22 mg/dL. This pattern points to impaired kidney function, since the high creatinine directly reflects reduced filtration rather than a transitory or non-renal factor.