Diagnosis: Diabetic Nephropathy
The diagnosis is A. Diabetic nephropathy. This patient with diabetes mellitus, hypertension, elevated creatinine, proteinuria, and normal-sized kidneys on ultrasound meets the clinical criteria for diabetic kidney disease (DKD).
Diagnostic Reasoning
The presence of proteinuria in a patient with long-standing diabetes and hypertension is sufficient to make a clinical diagnosis of diabetic nephropathy without requiring a kidney biopsy. 1 The American Diabetes Association specifically states that patients with type 2 diabetes, hypertension, and significant proteinuria (urinary albumin-to-creatinine ratio ≥300 mg/g) should be diagnosed with overt diabetic nephropathy. 1
Key Clinical Features Supporting Diabetic Nephropathy:
Proteinuria in the setting of diabetes: The presence of protein in the urine is a hallmark of diabetic kidney disease and indicates established renal parenchymal damage. 2 In most patients with diabetes, CKD should be attributable to diabetes if macroalbuminuria is present. 3
Elevated creatinine with reduced GFR: This indicates progressive diabetic nephropathy, consistent with the natural history of the disease where GFR begins to decline after the development of proteinuria. 1, 4
Normal kidney size: This is typical for diabetic nephropathy, which distinguishes it from chronic glomerulonephritis or other causes of CKD where kidneys are often small and scarred. 3 Normal-sized kidneys with proteinuria in a diabetic patient strongly support the diagnosis of DKD rather than other chronic kidney diseases.
Coexisting hypertension: Hypertension is present in approximately one-third of patients with type 2 diabetes at diagnosis and is commonly related to underlying diabetic nephropathy. 1 The BP of 130/90 mmHg reflects inadequately controlled hypertension in the context of kidney disease.
Why Not the Other Options:
Hypertensive Nephrosclerosis (Option B):
While this patient has hypertension, hypertensive nephrosclerosis typically presents with bland urinary sediment and minimal proteinuria (usually <1-2 g/day), not the significant proteinuria described here. 5 The combination of diabetes with substantial proteinuria makes diabetic nephropathy the primary diagnosis, even though hypertension may be contributing to kidney damage. 5
Polycystic Kidney Disease (Option C):
This diagnosis is excluded by the normal kidney size on ultrasound. Polycystic kidney disease would show bilaterally enlarged kidneys with multiple cysts on imaging, which is not present in this case. 3
Clinical Implications:
The diagnosis of diabetic nephropathy requires immediate initiation of renoprotective therapy with an ARB (such as losartan) or ACE inhibitor, targeting blood pressure <130/80 mmHg. 1 Additionally, glycemic control should be intensified toward HbA1c <7%, and protein restriction to <0.8 g/kg body weight per day should be implemented. 1 Given the elevated creatinine suggesting eGFR likely <60 mL/min/1.73 m², referral to a nephrologist is recommended. 1