Histopathological changes in cyclosporin-treated renal allografts biopsied at one and twelve months.

Forty-four renal allograft recipients were biopsied routinely one month and one year after transplantation. All patients received cyclosporin and prednisolone. Fifteen patients had at least one rejection episode, while 29 patients never underwent rejection. At one year there were no specific histological features that enabled these two groups to be distinguished. Between one month and one year, interstitial cellular infiltrate and vascular pathology regressed, and renal function steadily improved. Interstitial fibrosis, however, was either unchanged or mildly increased in all patients. There was no correlation between the amount of interstitial fibrosis at one year and either the total dose of cyclosporin or the mean concentration during the first 3 months. Our results suggest that trough, whole blood cyclosporin concentrations, at the upper level of the therapeutic range (800-200 ng/ml), may be safely tolerated during the first 3 months, with little evidence of chronic damage at one year. At one year maintenance doses of cyclosporin can be achieved that are associated with almost normal plasma creatinine concentrations and minimal tubular atrophy and interstitial fibrosis. We expect that such doses may be continued indefinitely.