Possible effect of time on renal allograft rejection.

The change in plasma creatinine concentrations from decreasing values after successful renal transplantation to increasing values after the onset of rejection occurs as a sudden event. Twenty-two such episodes in 16 renal allograft recipients were studied by extrapolating sequential measurements of plasma creatinine concentrations to see when the change occurred. Seventeen of the episodes occurred between 2300 and 1100 and the rest at other times. This difference was significant. The results suggest that rejection is more common at night and apparently has a circadian rhythm, being likely to first influence creatinine clearance at around 0600.