Diagnosis: Diabetic Nephropathy
The most likely diagnosis is A. Diabetic nephropathy. This 60-year-old woman with established diabetes mellitus, hypertension, lower limb edema, elevated creatinine, and significant proteinuria with normal kidney size presents the classic clinical picture of diabetic kidney disease 1, 2.
Clinical Reasoning
Why Diabetic Nephropathy is Most Likely
Established diabetes with proteinuria is the hallmark presentation of diabetic nephropathy, which characteristically progresses from microalbuminuria to overt proteinuria with declining renal function 1, 3.
Normal kidney size strongly supports diabetic nephropathy rather than chronic glomerulonephritis, as diabetic kidneys typically maintain normal or even enlarged size until very late stages, whereas chronic glomerulonephritis usually causes bilateral small kidneys 2.
The combination of diabetes, hypertension, and proteinuria creates the typical triad seen in diabetic nephropathy, where hypertension both contributes to and results from the underlying kidney disease 1.
Lower limb edema with proteinuria indicates nephrotic-range protein loss, which is characteristic of advanced diabetic nephropathy when glomerular filtration barrier dysfunction becomes severe 3, 4.
Why Other Options Are Less Likely
Hypertensive nephrosclerosis (Option D) is unlikely because it typically presents with bland urinary sediment and minimal proteinuria (usually <1 g/day), whereas this patient has significant proteinuria 2. Additionally, hypertensive nephrosclerosis would be an unusual primary diagnosis in a patient with established diabetes mellitus 2.
Chronic glomerulonephritis (Option C) is less probable given the normal kidney size on imaging—chronic glomerulonephritis typically causes bilateral renal atrophy and small kidneys 2. Furthermore, the absence of active urinary sediment (RBC casts, dysmorphic RBCs) or rapidly declining function makes primary glomerulonephritis unlikely 2.
Polycystic kidney disease (Option B) is excluded by the normal kidney size on imaging, as PCKD characteristically shows bilaterally enlarged kidneys with multiple cysts 2.
Important Clinical Considerations
Diabetic retinopathy screening is essential as its presence has 84-100% sensitivity for diabetic glomerulopathy and would further confirm the diagnosis 2.
The patient is already on valsartan (an ARB), which is appropriate therapy, but optimization of dosing and blood pressure control to <130/80 mmHg is critical to slow nephropathy progression 1, 2.
Quantify the degree of proteinuria with 24-hour urine collection or spot urine protein-to-creatinine ratio to establish baseline and monitor treatment response 1, 2.
Monitor for up to 20-30% increase in serum creatinine after optimizing RAS blockade, which reflects beneficial hemodynamic changes from reduced intraglomerular pressure rather than kidney damage 2.