[Correlations among the renal parenchymal components and renal function with IgA-GN; age related changes]

To clarify and evaluate the changes by aging to renal parenchyma of IgA nephropathy with normal renal function (serum creatinine levels less than or equal to 1.5 mg/dl), we compared morphological findings and renal function in 100 adult patients with IgA nephropathy similarly distributed in each decade of age including over 60 y.o.. The following histological parameters were investigated; glomerular sclerotic index calculated a mean for total glomeruli, tubulointerstitial damage or interstitial volume measured by the point-counting method, luminal narrowing index by intimal thickening of arterioles determined morphometry. Tubulointerstitial damages were significantly correlated to aging with a direct linear worsening. Luminal narrowing of arterioles rapidly worsened with age after 40 y.o. who were frequently associated with chronic hypertension. The patients over 60 y.o. had a significant correlation between luminal narrowing of arterioles and glomerular sclerotic index, though those were statistically no related in patients less than 60 y.o.. Glomerular sclerotic index was significantly related with tubulointerstitial damage at all decades except for thirtieth decade. Serum creatinine level was well correlated with glomerular sclerotic index and tubulointerstitial damage, respectively; increase of those indices may indicate poor prognosis. We concluded that ischemic glomerular sclerosis by mean narrowing of afferent arterioles may appear after 60 y.o., probably due to insufficiency of autoregulation for glomerular circulation. Luminal narrowing of arterioles in patients less than 60 y.o. may not reflect to be a main cause for ischemic damage of glomerulus. Therefore it may not be a indicator for renal prognosis in patients with IgA nephropathy less than 60 y.o.