Renal transplant uptake of technetium-99m sulfur colloid in various time periods after transplantation.

The uptake of technetium-99m sulfur colloid (TSC) by transplanted kidneys undergoing rejection has been described. In this retrospective study, the value of TSC uptake in diagnosing renal rejection was studied in different time intervals after renal transplantation. Within 14 days after transplantation, increasing uptake was seen in 88% of 26 rejection episodes. In patients with acute tubular necrosis, 42% of their studies showed TSC uptake. TSC did not predict rejection within the three days prior to rejection. Sensitivity, specificity and accuracy of 128 TSC studies were compared at different thresholds of TSC uptake; at best, accuracy was only 76%. In later time intervals, a much smaller percentage of patients had increasing uptake with rejection; this tendency was to remain unchanged. Many non-rejection studies showed some TSC uptake. In chronic rejection, persistently marked uptake dominated prior to one year after transplantation, but not beyond this. Thus, within 14 days after transplantation, TSC uptake may support the diagnosis of rejection. Thereafter its value becomes greatly limited.