Urinary cytology and the early detection of renal allograft rejection.

The appearance of pyroninophilic immunologically activated lymphocytes in the urine may be one of the earliest indications of acute rejection of a renal allograft. In a study of 50 allograft recipients there were 33 episodes of rejection within 1 month postoperatively. The presence of activated lymphocytes in the urine correlated with a clinical and biochemical diagnosis of rejection in 29 cases (88 per cent). In 20 cases (69 per cent) the activated lymphocytes were present at least 24 hours (median 2 days) before rejection was diagnosed by other means. In 2 patients (4 per cent) activated lymphocytes appeared in the urine without evidence of rejection, while 4 of 33 patients had rejection diagnosed and treated in the absence of lymphocyturia, for a false negative rate of 12 per cent. The 33 rejection episodes were treated by prednisolone and azathioprine. In 19 cases suppression of rejection correlated with the disappearance of pyroninophilic lymphocytes within 5 days, while in 10 persistent rejection was accompanied by persistent lymphocyturia. The presence of activated lymphocytes in the urine is a valuable early index of impending rejection in the transplanted kidney, and may be used with other clinical and biochemical criteria to detect the need for increased immunosuppression.