Radionuclide evaluation of renal transplant status

Abstract

Previous studies hav€ compared the usefulness of this data as well as blood and urine histamine levels with radionuclide studies such as the renogram, the hippurate clearance index, the radionuclide angiogram and quantitated sequential renal scintiphotos [5]. Of these methods the bladder/kidney ratio derived from quantitated scintiphotos was found to be the single most useful indicator of transplant function, and the most sensitive and reliable predictor of rejection [6]. This paper summarizes 5 years of experience and presents a practical protocol for radionuclide evaluation of transplant status, emphasizing the prediction of acute rejection and avoidance of certain pitfalls associated with the recommended.procedures. METHODRadionuclide studies were performed on a frequent basis on human renal homotransplant recipients for at least two weeks postoperatively. Serial scintiphotos were obtained with a Picker Dynacamera 2 with the patient in a supine position following 131 bolus intravenous administration of 300 4Ci of I-hippurate.Renogram and cystogram curves were then generated from magnetic tape recorded data. Simultaneously the blood disappearance rate RESULTS AND DISCUSSIONDuring a five year period 58b examinations were performed on 72 post-renal homotransplant recipients during the first 14 postoperative days. Results were analyzed as described under Method.In approximately 1/3 of these patients a clinically recognized rejection crisis, ranging from mild to severe, occurred during this period of time.The calculation of renogram indices was discontinued about half way through the study as being significantly less sensitive and less reliable than the remaining parameters to be discussed.The hippurate blood clearance index, although generally sensitive, was found to show transient paradoxical improvements just preceding rejection crisis about 50 per ceht of the time.. This phenomenon is apparently related to an outpouring of histamine, which may occur in the days prior to clinical rejection [10] and cause an increase in extravascular extravasation of hippurate. This index was found useful and is determined daily regardless of the general level of transplant function.The bladder/kidney ratio, derived from quantitated scinti-.photos at 20 minutes post-injection, not only proved to be the most sensitive indicator of transplant function, but in over 80%of all cases of early rejection there was a significant drop from 1 to 3 days before clinical rejection, as illustrated byIn acute rejection there was usually a temporary increase in the blood clearance index in association with the fall in bladder/kidney ratio. In delayed hyperacute rejection, associated with presensitization , there were simultaneous marked drops in the blood clearance index and the bladder/kidney ratio.In 20% of the cases in which there was no definite clinical evidence of a rejection crisis, there were transient false positive reductions in the bladder/kidney ratio occurring at the I end of'post-transplant diuresis. In most of these cases the...