SPECIFICITY OF INTERTUBULAR CAPILLARY CHANGES - COMPARATIVE ULTRASTRUCTURAL STUDIES IN RENAL-ALLOGRAFTS AND NATIVE KIDNEYS

The pathophysiology of chronic rejection of renal allografts is poorly understood and specific morphologic markers are being sought for its diagnosis. Ultrastructural splitting and reduplication of the basal la mina of the intertubular capillaries (ITCs) have been shown to be cons istently associated with transplant glomerulopathy (TG) in renal allog rafts and have been used as a marker of chronic allograft rejection. A lthough the presence of ITC abnormalities is extremely helpful diagnos tically and has been considered a surrogate for the diagnosis of TG wh en glomeruli are not available for examination, their specificity has not been tested. This study examined 135 biopsy specimens from renal a llografts and native kidneys and categorized the ITC basal lamina alte rations into 5 patterns. The results showed that although marked ITC b asal lamina abnormalities are characteristically seen in association w ith TG, lesser degrees of these changes may also be found in native ki dneys and in transplants with other types of glomerulopathies. in nati ve kidneys, splitting and reduplication of the ITC basal lamina were o bserved in cases of active lupus nephritis, membranoproliferative glom erulonephritis type I, crescentic glomerulonephritis, cryoglobulinemia , and hypertension. In allografts, ITC changes were seen in postinfect ious proliferative glomerulonephritis, acute cyclosporin toxicity, and hemolytic uremic syndrome, in addition to cases with TG. The histopat hologic diagnosis in renal diseases relies heavily on clinical, immuno fluorescence, and ultrastructural findings. Therefore, in the transpla ntation setting, with other less common pathological processes ruled o ut, the presence of abnormalities of the ITC basal lamina is highly in dicative of TG. This association is particularly true for cases with s evere ITC abnormalities.