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 histop athological and clinical parameters. Methods and results: Twenty allograft kidney biopsies from 19 patients, sho wing arteriolitis, were identified. Arterioles were defined as small vessel s with: (1) wall thickness of 1-3 myocytes; (2) diameter less than one-thir d of an adjacent glomerulus; and (3) discontinuous or absent elastica. Arte riolitis was defined as mural infiltration by lymphocytes. Other histologic al findings were categorized according to the Banff 1997 working formulatio n. Ten biopsies (50%) showed type IIA rejection, seven (35%) showed type I rejection, and three (15%) showed borderline change. Two patients with bord erline change had acute rejection in the next biopsy. None of the seven pat ients with type I rejection had previous or subsequent type II rejection on biopsy. A total 11/20 biopsies (10/19 patients) showing arteriolitis had t ype 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 sh own 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 arter iolitis were not encountered in this series.