Causes of albuminuria in patients with type 2 diabetes without diabetic retinopathy

Abstract

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 % Cl,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 A(1c), (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.