[Histopathological and functional study of the kidney in non-insulin dependent diabetes mellitus]

The histopathological characteristics of the kidney using light microscopy and immunofluorescence studies in samples obtained by renal percutaneous biopsy in 19 women and 7 men with non-insulin dependent diabetes mellitus (NIDDM) (mean of age: 55.07 +/- 9.04 yr and mean of "known" diabetes duration: 7.50 +/- 6.87 yr) were studied. The relationship with age, blood pressure, diabetic retinopathy and other complementary diagnostic methods such as serum creatinine (Cr), creatinine clearance (CrC), renal plasma flow (RPF), proteinuria and filtration fraction (FF) were also determined. Light microscopy studies detected 92.3% of patients with renal lesions of different degrees of severity. The presence and severity of glomerulopathy and arteriolopathy were related to diabetes duration (r: 0.764) and they were related to each other (rs: 0.773). In 2 patients, lesions were not observed and in 11 out of 14 patients with less than 5 yr of diabetes duration, mild lesions were detected. However, the histological changes became worse after that period. The glomerulopathy was also statistically correlated with Cr, CrC, RPF, proteinuria and FF. By immunofluorescence, fibrinogen, IgA and C3 were the most frequent and intense precipitates observed. They increased with diabetes duration and were located predominantly in the wall and the periphery of the glomerules and in renal tubules, suggesting that they originated by trapping. There were no precipitates in the mesenchyma, they were scarce in the interstice, Bowman's capsule and arterioles. Statistical correlation between diabetic histopathological renal changes and retinopathy was found. These results confirm that lesions in the kidney and retina in non-insulin dependent diabetic patients generally appear and evolve in a similar manner. Hypertension was diagnosed in 80.76% of patients, without statistical correlation between blood pressure and renal lesions. This suggests that at the onset, in non-insulin dependent diabetic patients hypertension and nephro-pathy are caused by different and independent pathogenic mechanisms. However, at an end stage, it seems that both situations can influence each other in a way that their evolution becomes more severe. Nephropathy in non-insulin dependent diabetes mellitus displayed scarce clinical signs and poor laboratory evidence except when the renal lesions become too severe. The lack of correlation between renal lesions and patients' age and blood pressure suggests the participation of diabetes at the onset of kidney structural impairment.