In a diabetic patient with impaired renal function and proteinuria but a normal retinal fundus, can this be considered diabetic kidney disease (DKD)?

Can This Be Considered Diabetic Kidney Disease (DKD)?

Yes, this can be considered diabetic kidney disease (DKD), particularly in type 2 diabetes where the absence of retinopathy does NOT exclude the diagnosis, though you should maintain heightened clinical suspicion for alternative or coexisting kidney pathology.

Key Diagnostic Framework

The most recent ADA guidelines 1 explicitly state that DKD may be present at diagnosis or without retinopathy in type 2 diabetes. This is a critical distinction from type 1 diabetes, where the absence of retinopathy makes DKD rare and should prompt investigation for non-diabetic kidney disease (NDKD).

Type 2 vs Type 1 Diabetes: Different Rules

• Type 2 diabetes: Retinopathy is only moderately sensitive and specific for DKD 2. The absence of retinopathy does NOT rule out DKD
• Type 1 diabetes: It is rare for patients to develop kidney disease without retinopathy 2, making absent retinopathy a red flag for NDKD

When to Suspect Non-Diabetic Kidney Disease

You should consider kidney biopsy or nephrology referral if ANY of these features are present 1, 2:

• Type 1 diabetes duration <5 years (or type 2 diabetes <5 years with sudden onset proteinuria 3)
• Active urinary sediment (RBCs >5/hpf, RBC casts, WBC casts)
• Rapidly increasing albuminuria or rapidly decreasing eGFR
• Nephrotic syndrome with sudden onset
• Gross hematuria
• Absence of retinopathy in type 1 diabetes specifically
• Severe renal insufficiency with minimal proteinuria (<500 mg/dL)

Clinical Predictors from Biopsy Studies

Recent research 3 found that among diabetic patients biopsied for suspected NDKD, 56% had pure NDKD and only 35% had true DKD. Key distinguishing features included:

• Shorter diabetes duration (<5 years) favored NDKD
• Shorter hypertension duration (4.98 vs 8.07 years) favored NDKD
• Absence of diabetic retinopathy was more common in NDKD

Practical Clinical Approach

For your patient with normal fundus:

1. Confirm the diagnosis is type 2 diabetes - if type 1, strongly consider nephrology referral for possible biopsy

2. Assess diabetes duration and clinical trajectory:

   • If diabetes >10 years with gradual progression → likely DKD
   • If diabetes <5 years with rapid onset → consider NDKD

3. Examine urinary sediment carefully:

   • Bland sediment without RBCs/WBCs → consistent with DKD
   • Active sediment → refer to nephrology

4. Monitor the clinical course:

   • Gradual, progressive decline → typical DKD pattern
   • Rapid deterioration → atypical, warrants investigation

5. Treat as DKD while maintaining vigilance:

   • Initiate SGLT2 inhibitors, ACE inhibitors/ARBs, and consider finerenone 1
   • Refer to nephrology if eGFR <30 mL/min/1.73 m² or continuously worsening parameters 1

Critical Caveat

The absence of retinopathy in type 2 diabetes is common and does not preclude DKD diagnosis 2. However, it should lower your threshold for nephrology referral if other atypical features emerge. Studies show that up to 56% of diabetic patients with atypical presentations have NDKD 3, which may require different treatment (including immunosuppression for conditions like IgA nephropathy or acute interstitial nephritis).