Clinical Science Histomorphological Assessment of Phlebitis in Renal Allografts

Aim To evaluate the histomorphological features of veins in normal and transplanted kidneys. Methods Between 1992 and 1997, we semiquantitatively evaluated histomorphological changes in veins in nephrectomy specimens of 29 renal allografts with rejection and in 31 control kidneys. The structure of different segments of renal veins was additionally analyzed. Results Small interlobular veins were composed of endothelium and basement membrane, similar to capillaries, while the walls of large in-terlobular and arcuate veins had smooth muscle cell bundles forming the medial layer, similar to large extrarenal veins. In the control group, only focal mononuclear infiltration around small interlobular veins was found (8/31). In rejected kidney allografts, the veins were frequently infiltrated with inflammatory cells, predominantly T lymphocytes and macrophages (29/29). Other changes included thrombosis (16/29), fi-brinoid necrosis (7/29), and sclerosis (9/29), and in one case an intimal lipid deposition. Conclusion This study, performed on whole explanted kidney speci-mens, revealed that rejection vasculitis often involved extrarenal and intrarenal veins, showing a whole spectrum of histopathological chang-es similar to those in arteries. Since large intrarenal veins have a muscle wall, we believe that the term “rejection phlebitis ” could be used in re-nal transplant pathology