ORIGINAL ARTICLE The renal transplant score - a different way of evaluating renal transplant pathology Abstract The renal transplant is a notoriously difficult organ to assessfor pathology. Radionuclide imaging can help, but, although sensitive, the evaluation is not very specific. For this reason, a different approach was used to examine renal images and resuIts were correlated with histology. The transplant score is determ ined from images of perfusion RPClauss MBChB, MMed(NucMed), Nuclear Medicine Department, A Kobryn Specialist in Generaf Surgery, Surgery Department, both at MEDUNSA. / 16 SA JOURNAL OF RADIOLOGY- June 1997 and function on certain criteria such as time of appearance of the kidney after tracer injection, intensity of background, size and homogeneity of tracer uptake by the kidney. Although small, the pilot study could distinguish between hyperacute rejection, acute rejection, chronic rejection and cyclosporin toxicity. Introduction Attempts have previously been made to detect renal transplant pa- thology scintigraphic ally, usually with 99mm Tc DTPA. The most success- ful of these is probably the perfusion index.l" Others include functional imaging' and fractional mean transit time." With all these aids at hand, di- agnosis of renal transplant pathology is still difficult. Serial scintigraphy of both perfusion and function often over a period of days or weeks is necessary for decent monitoring of the progress in renal transplants. To aid the detection of pathology in renal transplants, a different ap- proach to reading the scintigram was tested, based on renal and background information on the scintigram. Renal perfusion, uptake and excre- tion using 99m Tc Glucoheptonate to page 17 The renal transplant score- a different vvav of evalu<'lting renal transplant pathology (rampage 16 was scored on selected criteria. The score was compared to the histologi- cal diagnosis of various transplants. Glucoheptonate was chosen for inter- pretation of function (perfusion and early excretion) and parenchymal in- tegrity (delayed views after furosem- ide injection). Method Eight renal transplants were imaged using 99m Tc Glucohep- tonate and biopsied within 24 hours of the scintigraphy for histological diagnosis. 150 MBq of 99m Tc Glucohep- tonate were injected into an antecu- bital vein while a dynamic acquisition of 60 frames of one second was in progress, anterior to the patient. The camera field of view included the re- nal transplant, large blood vessels, spleen, ureter and bladder. The first acquisition phase was immediately followed by a second phase of 120 frames of 15 seconds, imaging kidney function. A delayed static view of the transplant was ac- quired 3 hours later after 20 mg furo- semide injection. The perfusion frames were com- bined to 15 frames of 4 seconds and the 120 frames of function were com- bined to 15 frames of 2 minutes. A renogram was generated and frames were displayed, assessed and scored for perfusion, uptake and excretion. Perfusion criteria (phase I) included: Background score: o - Photopenic region in place of kidney 1 - Maximal kidney intensity equal to background 2 - Maximal kidney intensity between background and liver 3 - Maximal kidney intensity same as maximal liver perfusion 4 - Maximal kidney intensity better than maximal liver perfusion Iliac vessels score: o - Photopenic region in place of the kidney 1 - Tracer bolus reaches kidney after it reaches iliac vessels 2 - Tracer bolus reaches kidney before it reaches iliac vessels Liver score: o - Photopenic region in place of the kidney 1 - Maximal kidney perfusion after maximal venous liver perfusion 2 - Maximal kidney perfusion before maximal venous liver perfusion Maximum perfusion score: 4+2+2=8 Function criteria (phase 2) included: Background score: o - Photopenic region in place of kidney 1 - Maximal kidney uptake equal to background 2 - Maximal kidney uptake with prominent background 3 - Maximal kidney uptake with minimal background Renogram score: 0- No peak on renogram 1 - Peak after 4 minutes 2 - Peak before 4 minutes Homogeneity score: 0- No kidney seen on delayed image 1 - lnhomogenous tracer uptake on delayed image 2 - Homogenous tracer uptake on delayed image Size score: 0- No kidney seen 1 - Small kidney 17 SA JOU RNAL OF RADIOLOGY. Ju ne 1997 2 - Normally sized kidney Elimination score: o - No kidney seen 1 - Elimination half life from region of interest over the heart> 100 min 2 - Elimination half life from region of interest over the heart of 50-100 min 3 - Elimination half life from region of interest over the heart < 50 min Maximum function score: 3 + 2 + 2 + 2 + 3 = 12 Results Table I shows the perfusion scores for the various patients. Table II shows the function scores for the same group of patients. Perfusion and uptake of tracer in acute and hyper-acute trans- plant rejection are seen in Figures 1 Figure la: Fifteen frames of 4 seconds showing the perfusion of a renal transplant undergoing acute rejection. Figure 1b: Fifteen frames of 2 minutes showing the function of a renal transplant undergoing acute rejection. to page 18 The renal transplant score- a different vvay of evaluating renal transplant pathology (rom page 17 Table I: Perfusion scores of patients with various transplant pathologies Table II: Function scores of patients with various transplant pathologies Name EM AK JT PM JM as MS AM Name EM AK JT PM JM as MS AM Background 2 2 0 2 Background 2 Iliac 2 0 Peak 2 Liver 2 0 Homogeneity 0 Size 0 Total 5/8 4/8 6/8 4/8 3/8 7/8 4/8 Elimination 1 0 % Total 63% 50% 75% 50% 38% 88% 0% 50% Total 7/12 8/12 8/12 7/12 6/12 9/12 0/12 10/12 Diagnosis cr er cr er ar norm har ct Percentage 58% 67% 67% 58% 50% 75% 0% 83% Diagnosis er er er er ar norm har ct er chronic rejection nonm - nonmal ar acute rejection ct - cyclosporin toxicity er - chronic rejection norm - normal har hyper-acute rejection ar - acute rejection ct - cyclosporin toxicity har - hyper-acute rejection Figure 28: Fifteen frames of 4 seconds showing the perfusion of 8 renal transplant undergoing hyper-acute rejection. Figure 2b: Fifteen frames of 2 minutes showing the function of a renal transplant undergoing hyper-acute rejection. and 2. Figure 3 shows the renogram and the half life of tracer in the blood from a region of interest over the heart Figure 4: Bar diagram showing the perfusion and function scores in patients with various transplant pathologies. Figure 3b: Half life of tracer in the blood from a region of interest over the heart in a transplant undergoing acute rejection reportedS,6,7,8 and can be seen in our study.The perfusion score as estimated in our patient group showed a clear difference between the normal trans- plant, acute and chronic rejection. Attempts have been made previously to use sulphur colloid to predict trans- plant rejection. These were however unsuccessful." It has been shown previously that cyclosporin toxicity causes parenchymal tracer retention but does not impair perfusion." Such patient presented with a moderate perfusion but good function score in our study. In hyper-acute rejection there was no perfusion or uptake of the tracer. in a patient with acute rejection. Fig- ure 4 is a bar diagram that compares perfusion and function scores (con- verted to percent) for various trans- plant pathologies. Perfusion and function score of renal transplants with various pathologies. Norm eye ehr rej Pathologies _ perlualon ~ function acute rej Our pilot study suggests that a renal transplant score may be a way to distinguish renal transplant pathology. Further evaluation of score criteria and exploration of the method with different tracers is necessary. Conclusion Figure 3a: Renogram of a transplant undergoing acute rejection. Discussion Perfusion scintigraphy is a good indicator for acute rejection in renal transplants. This has often been 18 SA JOURNAL OF RADIOLOGY. June 1997 References 1, Anaise D, Oster ZH, Atkins HL, Arnold AN, Weis S, Waltzer WC, Rapaport FT. Cortex Perfusion Index: A sensitive detector of acute rejection crisis in transplanted kidneys. J Nucl Med 1986; 27: 1697-1701,:,,", __ -:- _ topage23