Intertubular capillary changes in the cortex and medulla of transplanted kidneys and their relationship with transplant glomerulopathy: an ultrastructural study of 12 transplantectomies.

Twelve kidney allografts removed 3 to 98 months (mean, 44.8 months) after transplantation were investigated. The presence and severity of intertubular capillary changes, which were characterized by splitting and multilayering of the basement membrane, were carefully noted. These changes were graded as mild, moderate, and severe according to the number of basement membrane layers. They were found in both cortical and medullary capillaries in all but one kidney and were always associated with transplant glomerulopathy. Ultrastructural changes observed in the glomeruli and capillaries were similar, suggesting that they share the same pathogenetic mechanisms, probably connected to immune-mediated endothelial cell damage. Although glomeruli can be absent in small biopsy specimens, intertubular capillaries are easily detectable. Because capillary changes can be considered a marker of transplant glomerulopathy, which is known to have ominous prognostic significance, the identification of such changes acquires clinical relevance. Electron microscopic investigation is therefore strongly advisable whenever a renal biopsy is performed to identify transplant glomerulopathy.