Renal changes in long-term type 1 (insulin-dependent) diabetic patients with and without clinical nephropathy: a light microscopic, morphometric study of autopsy material.

The relationship between clinical diabetic nephropathy and morphological renal changes was studied in autopsy material from 34 long-term Type 1 (insulin-dependent) diabetic patients of juvenile onset. Seventeen had no clinical signs of nephropathy (defined by persistent proteinuria, hypertension, and elevated serum creatinine) while a further 17 age-matched diabetic patients with a similar duration of diabetes had severe clinical nephropathy. The renal tissue was examined by morphometric light microscopy, using a point counting technique and the results compared with renal tissue from subjects who died without diabetes. In the diabetic patients without clinical nephropathy, arteriolohyalinosis was much more pronounced compared with non-diabetic subjects (2p< 0.001) and within the glomeruli the amount of subcapsular fibrosis and glomerular mesangium was increased (2p < 0.05 and < 0.001, respectively). The area of open capillaries was decreased compared with non-diabetic subjects (2p < 0.025), and the percentage of occluded glomeruli was significantly increased (2p< 0.05). The diabetic patients with clinical nephropathy had significantly more interstitial tissue and glomerular mesangium (2p < 0.001) and less open glomerular capillaries (2p < 0.001) than diabetic subjects without clinical nephropathy, but severe glomerulosclerosis could be seen in the diabetic patients without any sign of clinical nephropathy. Serum creatinine correlated with the mesangial area (r = 0.792, 2α < 0.001). No difference was observed between the two diabetic groups regarding the degree of arteriolohyalinosis, the number of Kimmelstiel-Wilson lesions or exudative lesions. A significant negative correlation existed between the relative area of open capillaries and the relative area of mesangium (r =-0.86, 2α <0.001). Remarkable mesangial enhancement was present in most of the diabetic patients with, but also in several diabetic subjects without, clinical nephropathy. On the other hand, the area of open capillaries was within the normal range in most of the patients who did not show any clinical sign of nephropathy. Thus, preservation of a normal area of open capillaries in renal tissue from long-term diabetic patients with glomerulosclerosis seems to be a good light microscopic indicator of absence of clinical nephropathy.