The relationship of untreated borderline infiltrates by the Banff criteriato acute rejection in renal allograft biopsies

The relationship of borderline infiltrates to acute rejection by Banff crit eria in renal allografts of patients receiving only maintenance immunosuppr ession is not clear. Renal allograft biopsies with borderline lesions that were not treated with additional anti-rejection therapy were retrospectivel y studied. Sixty-five such biopsies were identified from 50 patients, and t heir outcome was determined by serum creatinine and/or histologic findings in subsequent biopsies, up to 40 d after the initial biopsy. In addition to the borderline infiltrates, there was evidence of acute cyclosporine or ta crolimus toxicity (58%), acute tubular necrosis (12%), and urinary obstruct ion (12%). Forty-day follow-up after 30 (46%) biopsies revealed serum creat inine <110% of baseline, and repeat biopsies were not indicated, In 17 (26% ), the serum creatinine initially decreased, then increased, and follow-up biopsies showed acute rejection in nine. In 18 (28%), the creatinine remain ed elevated and follow-up biopsies revealed acute rejection in nine. The un treated borderline infiltrates were thus nonprogressive after 47 biopsies ( 72%) and progressed to histologic acute rejection after 18 (28%). When ther e was increasing or persistently elevated creatinine after the initial biop sy, 51% of cases (18 of 35) progressed to acute rejection. Infiltrates that progressed to rejection had more frequent glomerulitis (7 of 18 versus 3 o f 47, P = 0.003) and Banff acute score indices (i+t+v+g) >2 (16 of 18 versu s 29 of 47, P = 0.03). A majority (72%) of borderline infiltrates not given additional anti-rejection therapy did not progress to acute rejection over 40 d of follow-up, suggesting that conservative management of these lesion s, at least in the short term, may be more appropriate than routine treatme nt as acute rejection.