Chronic allograft nephropathy--biopsy findings and outcome.

Background: Chronic allograft nephropathy (CAN) is a composite term for various types of damage to a kidney transplant. We wanted to analyse its components in relation to baseline biopsy findings, transplant function, and outcome.

Methods: Among renal transplantations performed from 1985 to 1997, 156 were identified where allograft biopsies had been obtained on clinical indication 6 months after transplantation or later, baseline biopsies were available in each case and the patient's original disease was known. Time after transplantation was median 2.2 years (range 0.5-13). The biopsies were reviewed and the Banff 1997 CAN score obtained.

Results: All but one late biopsy showed some CAN grade, 48% grade II, and 7.5% grade III. Acute tubulointerstitial rejection was seen in 9% but vascular rejection in only 3%. Arterial wall thickening was present in 66% of the late biopsies, correlated with donor age and its presence at baseline but also with time after transplantation. The Banff CAN score and serum creatinine level were both independent predictors of further graft survival, relative risk 0.35 (confidence interval 0.15-0.82, P=0.015) for CAN grade I vs III and 0.30 (0.14-0.67, P=0.003) for serum creatinine <170 vs >250 micromol/l. Presence of arterial wall thickening had no prognostic impact.

Conclusion: The CAN grade is predictive of further graft survival independently of the serum creatinine level. Interstitial fibrosis and tubular atrophy are more prominent features of chronic graft damage than vascular rejection. Unspecific arterial wall thickening is partly dependent on baseline conditions and lacks prognostic impact in this late stage.