A 75-year-old woman with osteopenia has decreased creatinine clearance over 10 years but stable weight and no overt kidney disease. Which is the most likely cause of the decreased creatinine clearance?

• A. Normal aging
• B. Hypertensive nephrosclerosis
• C. Diabetic nephropathy
• D. Acute kidney injury

Answer: (C)

Renal function declines with age, so a gradual decrease in creatinine clearance in a 75-year-old without overt kidney disease fits aging-related changes in glomerular filtration rate. As people get older, there’s a loss of nephrons and renal mass, and GFR tends to fall over decades. This can lower creatinine clearance even when weight is stable and there are no other signs of kidney disease. Also, reduced muscle mass in the elderly can decrease creatinine production, which can mask changes in serum creatinine, making clearance measurements particularly important to detect true declines in filtration.

If the decline were due to a disease process, you’d expect additional clues: hypertensive nephrosclerosis often comes with a long history of hypertension and may show signs of kidney damage such as proteinuria; diabetic nephropathy would require diabetes with progressive albuminuria and kidney impairment; acute kidney injury would present as a sudden drop in kidney function rather than a slow, decade-long change.