Causes of Albuminuria in Patients with Type 2 Diabetes Without Diabetic Retinopathy

Background: The causes of albuminuria in patients with type 2 diabetes are heterogeneous and are scantily investigated, particularly if the patient has a lack of diabetic retinopathy. Therefore, we evaluated the structural background of albuminuria in a large consecutive group of Caucasian patients with type 2 diabetes without retinopathy.

Methods: Three hundred forty-seven consecutive patients with type 2 diabetes with persistent albuminuria (>300 mg/24 h) were recorded. Fundus photo (80%) and ophthalmoscopy were performed. Ninety-three (27%) had no retinopathy, and a kidney biopsy was performed in 52 (56%) of these patients. An insufficient tissue sample was obtained in one patient. The biopsies were evaluated by three masked nephropathologists.

Results: The biopsies revealed diabetic glomerulopathy in 69% of the patients (28 males and 7 females), while the remaining 31% (95% CI, 18 to 44) had either nondiabetic glomerulopathies such as glomerulonephritis (N = 7, 6 males and 1 female, 13%) or normal glomerular structure (N = 9, 7 males and 2 females, 18%). No significant differences in sex, age (56 +/- 8 vs. 53 +/- 10 years, mean SD), body mass index (30 +/- 4 vs. 31 +/- 8 kg/m2), known duration of diabetes (6 +/- 6 vs. 4 +/- 3 years), GFR (95 +/- 29 vs. 89 +/- 31 mL/min/1.73 m2), albuminuria (1304 +/- 169 to 4731 vs. 1050 +/- 181 to 5176 mg/24 hours), blood pressure (150/87 +/- 16/9 vs. 145/89 +/- 16/9 mm Hg), prevalence of hypertension (89 vs. 100%), hemoglobin A1c (8.2 +/- 1.6% vs. 9.0 +/- 2.5%), and serum total cholesterol (7.1 +/- 2.4 vs. 6.3 +/- 1.6 mmol/L) were found between patients with and without diabetic glomerulopathy.

Conclusions: Albuminuric patients with type 2 diabetes without diabetic retinopathy have a prevalence of biopsies with normal glomerular structure or nondiabetic kidney diseases of approximately 30%. A separation between diabetic and nondiabetic glomerular lesions was not possible based on demographic, clinical, or laboratory data. Consequently, such patients may require further evaluation, including a kidney biopsy.