Membranous glomerulonephritis: a morphometric study.

Archival material from 45 renal biopsies with a diagnosis of idiopathic membranous glomerulonephritis (MGN) were studied by computer-aided image analysis in order to evaluate the prognostic significance of glomerular and interstitial morphometry in MGN. The control group consisted of thirty seven normal renal biopsy specimens. The surface area, the perimeter, the major axis length and the shape factor of renal glomeruli as well as the percentage of the interstitial fibrosis were measured. All the morphometric parameters related to the size of glomeruli had significantly higher values in the patient group (p = 0.000 for all the parameters). However, no significant difference of the glomerular size between different stages of MGN was observed. In contrast, the percentage of interstitial fibrosis increased as the MGN stage rose (median values: 10.3% in stage 1, 14.2% in stage II, 26.9% in stage III, 28.9% in stage IV and 34.2% in stage V, Kruskal-Wallis ANOVA H = 37.645, p = 0.000). In the multivariate analysis the percentage of interstitial fibrosis was the only independent prognostic factor (p = 0.013). Our findings suggest that, in membraneous glomerulonephritis, the interstitial fibrosis increases as the MGN stage progresses, while the size of renal glomeruli has increased at a very early stage of the disease. This fact may indicate that interstitial fibrosis, not glomerular lesions, is mainly responsible for the reduction of renal function.