Arteriolitis in renal transplant biopsies is associated with poor graft outcome

AIMS: The Banff 1997 classification of renal allograft pathology identifies arteriolitis as a finding of uncertain significance. We sought to improve our understanding of arteriolitis by correlating its occurrence with histopathological and clinical parameters. METHODS AND RESULTS: Twenty allograft kidney biopsies from 19 patients, showing arteriolitis, were identified. Arterioles were defined as small vessels with: (1) wall thickness of 1-3 myocytes; (2) diameter less than one-third of an adjacent glomerulus; and (3) discontinuous or absent elastica. Arteriolitis was defined as mural infiltration by lymphocytes. Other histological findings were categorized according to the Banff 1997 working formulation. Ten biopsies (50%) showed type IIA rejection, seven (35%) showed type I rejection, and three (15%) showed borderline change. Two patients with borderline change had acute rejection in the next biopsy. None of the seven patients with type I rejection had previous or subsequent type II rejection on biopsy. A total 11/20 biopsies (10/19 patients) showing arteriolitis had type IIA rejection in the index or next biopsy. On follow-up, graft loss due to rejection occurred in 5/19 (26%) patients (median 126 days); all had shown type IIA rejection on a previous biopsy. Chronic allograft nephropathy developed in a further 4/19 (21%) patients (median 157 days), of whom three had shown only type I rejection on biopsy. CONCLUSION: Arteriolitis is associated with acute rejection, often type II rejection, and is associated with poor graft outcome. Other causes of arteriolitis were not encountered in this series.