Computerized technique for evaluating renal transplant function

This investigation was undertaken to improve the assessment of renal transplant function in the early post-operative period when the usual measures of renal function afford little useful information. A simplified mathematical model of I-131 hippurate transport allows separation of renal uptake and excretion. Uptake (U) is defined as the fraction of I-131 hippurate in the plasma picked up by the kidney per minute, and excretion (E), the fraction of I-131 hippurate in the kidney excreted into the bladder per minute. Scintillation camera data from the region of the renal allograft are framed at 4/min by a computer system for up to 30 minutes post injection. After regions of interest are flagged over the kidney, bladder and background regions, the activity-time curves are analyzed, and values for U and E are output in a report updated through punched paper tape for any values from previous studies. The entire analysis of a patient study requires about 5 minutes of technologist time. Over 150 studies on 24 patients have been analyzed using the above technique. In the immediate post-operative state when anuria or severe oliguria is often present, sequential estimation of U was found to be a sensitive measure of renal transplant viability. In the period beyond one week reductions in U and E appeared to be sensitive measures of rejection, while increases in U and E heralded amelioration of the rejection episode. Changes in U and E appeared to be more sensitive measures of changes in renal function than routine qualitative scintiphotographic analysis. This technique has proven useful in following the renal function status of the kidney transplant recipient through acute tubular necrosis and rejection episodes and has been a significant adjunct to routine scintigraphy