Posttransplant renal rejection: comparison of quantitative scintigraphy, US, and MR imaging

Accuracy of ultrasonography (US), quantitative scintigraphy, and magnetic resonance (MR) imaging in diagnosis of acute renal allograft rejection was studied in 46 patients who underwent renal biopsy. Thirty-three patients had acute rejection; six, cyclosporine nephrotoxicity, as shown by biopsy, clinical findings, and follow-up study; two, acute tubular necrosis; and five, normal biopsy findings and renal function. Accuracy in demonstrating rejection was 72% for US and 75% for scintigraphy, indicating no significant difference between the two. MR imaging was significantly more accurate, reaching a level of 98%. However, accuracy of MR in demonstrating acute tubular necrosis in a larger number of patients is not known, and its accuracy in indicating recurrent glomerulopathy or infectious disease has not been addressed. The definitive role of MR in evaluating posttransplant renal failure is currently not established, but because of its high sensitivity in detecting renal abnormality, MR can be used for cases when results of US or scintigraphy are equivocal or contradict clinical impressions or when biopsy cannot be performed for medical reasons.     

Report of the radionuclides in nephrourology committee for evaluation of transplanted kidney (review of techniques)

Comprehensive evaluation of renal transplants has been important in differential diagnosis of medical and surgical complications in the early post-transplantation period and in the long-term follow-up. If performed well, it yields excellent functional and good anatomic information about the graft that can be effectively used in the patient. That includes selection of patients for biopsy and for various drug regimens. This is true especially in patients with anuric acute tubular necrosis (ATN) and in patients with developing chronic rejection. Improving indices of renal function (effective renal plasma flow, uptake of tubular tracers) can indicate resolution of tubular injury (ATN) while there is still no improvement in plasma creatinine. In patients with chronic rejection, plasma creatinine increases only after approximately 30% of renal function is lost due to graft fibrosis. Early recognition of this condition could permit treatment and delay of retransplantation. The protocol recommended at the Copenhagen meeting includes a flow study, scintigram of the kidneys, prevoid and postvoid bladder image, injection site image (quality control), time/activity curves of the graft and bladder, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the graft could be performed either with 99mTc mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Quantitative analysis of perfusion facilitates interpretation of the study during the early post-transplantation period. ATN, common in cadaver transplants, typically shows adequate perfusion. The function phase should include images and time/activity curves. Images alone are insufficient. Quantitative data such as clearance or other indices of function and indices of tracer transit are essential for correct interpretation of the results. Normal images and normal graft function reliably exclude clinically important complications. A single scintigram demonstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor perfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chronic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensin converting enzyme challenge) should be used whenever indicated.     

99mTc-DTPA renal studies for acute tubular necrosis: specificity of dissociation between perfusion and clearance

In order to evaluate the usefulness of radionuclide renal studies in differentiating acute tubular necrosis from other causes of decreased renal clearance (e.g., rejection) in renal transplant patients, we assumed that acute tubular necrosis would be common during the first 4 days after cadaveric transplantation (group 1) and uncommon 3 weeks or longer after transplantation (group 2). There were 38 renal studies in 34 patients in group 1 and 62 studies in 27 patients in group 2. Each renal study consisted of both a technetium-99m-DTPA and an iodine-131-hippuran study. Perfusion, clearance, and transit time in the 99mTc-DTPA study, and clearance and transit time in the 131I-hippuran study were visually graded on a 5 point scale without knowledge of the time of study or clinical diagnosis. There were 19 studies in group 1 and 25 studies in group 2 with clearance decreased two or more gradations. Eleven 99mTc-DTPA studies had perfusion 2 or more gradations better than clearance; all 11 were in group 1 (p less than 0.01). Other dissociations within the 99mTc-DTPA and 131I-hippuran studies, or between them, did not distinguish the two groups. Data support the hypothesis that decreased clearance with relatively well preserved perfusion in 99mTc-DTPA studies is common in acute tubular necrosis and uncommon in other causes of decreased renal clearance.     

Acute renal allograft rejection: difficulty in diagnosis of histologically mild cases by MR imaging

To determine the ability of magnetic resonance (MR) imaging to diagnose various degrees of acute allograft rejection (AR), 33 MR examinations in 28 patients were obtained. Surface coils were used in 21 examinations. Seventeen examinations were correlated with biopsy results, which were graded as absent (n = 7), mild (n = 6), or severe (n = 4) AR. Corticomedullary differentiation (CMD) on T1 weighted images was graded as absent/poor versus distinct, and images were also evaluated for visibility of intrarenal vessels. For serial examinations, renal volume was measured and compared. The MR results were correlated with radionuclide interpretations in 22 cases. Diminished CMD was most common with AR (7 of 12) but was also seen with acute tubular necrosis (2 of 6) and cyclosporin toxicity (2 of 3). All four cases of severe AR had diminished CMD. In contrast, only one of six cases of mild AR had diminished CMD (p less than 0.05). Four of five cases of mild AR by radionuclide scan were correctly diagnosed. Visualization of intrarenal vessels was best with surface coils, but this did not contribute to differential diagnosis. Renal volume was increased in rejecting allografts. Magnetic resonance is a promising modality for investigation of renal allografts but is not a sensitive or specific modality for the diagnosis of mild AR.     

Renal transplant sonography: correlation of Doppler and biopsy results in cellular rejection.

Seventy-one patients with allograft dysfunction had concomitant Doppler sonography and percutaneous biopsy. Forty-one had biopsy proven acute cellular rejection and eight had acute cellular rejection in combination with acute tubular necrosis. Real time ultrasonic appearance and various parameters of Doppler waveform were studied and compared with 30 controls who had a long period of stable function with no previous episodes of rejection or acute tubular necrosis (ATN). Morphological appearances were unhelpful in diagnosing rejection. A resistive index greater than 0.8 in the study group was highly specific for dysfunction but could not differentiate between acute rejection and ATN. However, two patients in the control group of normal transplants had a resistive index of 0.83. An early to mid diastolic notch was highly specific for acute rejection but of low sensitivity. It may be the only Doppler indication of cellular rejection and may be present when the resistive index is in the normal range.     

Value of urinary cytology findings in the diagnosis of acute renal graft rejection

BACKGROUND: Acute rejection of allograft is one of the most serious complications of renal transplantation that requires fast and precise diagnostic approach. In this paper our experience in cytologic urinalysis as a diagnostic method of the acute renal allograft rejection was reviewed. METHODS: The study group included 20 of 56 patients with transplanted kidneys who were assumed for the acute allograft rejection according to allograft dysfunction and/or urine cytology findings. Histological findings confirmed allograft rejection in 4 patients. Urine sediment obtained in cytocentrifuge was air-dried and stained with May-Grunwald-Giemsa. Acute allograft rejection was suspected if in 10 fields under high magnification 15 or more lymphocytes with renal tubular cells were found. RESULTS: Acute transplant rejection occurred in 32.1% patients. In 15 patients clinical findings of the acute renal allograft rejection corresponded with cytological and histological findings (in the cases in which it was performed). Three patients with clinical signs of the acute allograft rejection were without cytological confirmation, and in 2 patients cytological findings pointed to the acute rejection, but allograft dysfunction was of different etiology (acute tubular necrosis, cyclosporine nephrotoxicity). In patients with clinical, cytological and histological findings of the acute allograft rejection urine finding consisted of 58% lymphocytes, 34% neutrophilic leucocytes and 8% monocytes/macrophages on the average. The accuracy of cytologic urinalysis related to clinical and histological finding was 75%. CONCLUSION: Urine cytology as the reliable, noninvasive, fast and simple method is appropriate as the a first diagnostic line of renal allograft dysfunction, as well as for monitoring of the graft function.     

The role of nuclear cardiology procedures in the evaluation of cardiac function following heart transplantation

Heart transplantation is, today, an accepted and recommended modality in the management of selected patients suffering from terminal heart disease. However, acute rejection and infection remain the major complications of this operation. Serial endomyocardial biopsy (EB), considered as the standard for diagnosis of cardiac rejection, is an invasive and delicate operation, not free of complications, even when done by skilled personnel in specialized centers. The object of this study was to compare and correlate between radionuclide ventriculography (RNV) and the histologic findings of EB. Furthermore, to validate the use of nuclear cardiology techniques that allow noninvasive, reliable, and rapid quantitation of ventricular function and myocardial perfusion for the diagnosis and management of rejection in patients with heart transplants. Radionuclide studies of left ventricular function were performed in 3 heterotopic heart transplant patients (HHT) with long term survival and early after the operation in 5 patients with HHT, 12 orthotopic heart transplants (OHT) and in 2 heart and lung transplants (HLT). Simultaneous EBs were performed in the early posttransplant patients and a histologic score for acute rejection was obtained. First pass (FP) and multigated equilibrium blood pool ventriculography, using the in vivo 99mTc-labelling of RBCs was used to measure left ventricular volumes (LVV) such as stroke volume (SV), end-diastolic volume (EDV), end-systolic volume (ESV), and both global and regional ejection fraction (EF, REF). The histological grading of acute rejection was classified into four groups: (1) no rejection, (2) mild rejection, (3) moderate rejection, and (4) severe rejection. The median of each LVV parameter was calculated and correlated with the EB using a nonparametric one way analysis of variance. A percentage change of LVVs was used rather than the difference of the calculated LVVs. During moderate acute rejection, SV had the highest correlation in P less than 0.004, followed by the EDV (P less than 0.05), and finally ESV (P less than 0.02). During severe acute rejection the correlation was SV (P less than 0.0008), EDV (P less than 0.001), and ESV (P less than 0.006). Myocardial perfusion scintigraphy using 201T1 was performed in the HHT patients, although, at this stage we have not attempted a correlation with the histologic findings. In one patient with long term survival OHT, increased 131I-metaiodobenzylguanidine (MIBG) myocardial uptake was evident during a rejection episode.     

Renal transplant dysfunction: MR evaluation

The results of 45 MR examinations were prospectively compared with the clinical course and biopsy results in 38 renal transplant patients to determine the role of MR in evaluating allograft dysfunction. Twenty-six patients underwent allograft biopsy. In eight patients in whom the biopsy was performed more than 48 hr after MR examination and in 19 patients who did not have a biopsy, the subsequent clinical course was sufficiently diagnostic to determine the specific cause of the transplant dysfunction. Corticomedullary differentiation, graded from 0 to 3, was not helpful in separating rejection (n = 20) from acute tubular necrosis (n = 9), drug toxicity (n = 7), pyelonephritis (n = 2), or normal grafts (n = 7) because of overlap between groups (sensitivity =; 60%, specificity = 60%). In the six patients with two or more MR studies, serial changes in corticomedullary differentiation were not consistent and could not be used to diagnose rejection. When any abnormality of allograft sinus fat, size or shape, or corticomedullary differentiation was considered, the sensitivity for the diagnosis of rejection approached 80%; however, specificity was low (48%). We conclude that MR imaging is not sufficiently accurate to replace transplant biopsy and therefore has a limited role in the evaluation of transplant dysfunction.     

Incidental recognition of left subclavian vein obstruction on renal scintigraphy.

In a renal transplant recipient with persistently poor graft function, the flow phase of a renal scan incidentally revealed multiple venous collaterals with focally increased vascular activity near the left lobe of the liver (quadrate lobe). This was initially assumed to represent superior vena cava (SVC) obstruction. A renal biopsy was contemplated to exclude acute rejection because of a nondiagnostic flow phase (loss of a bolus effect). However, because the possibility of venous obstruction at the level of the subclavian and/or brachiocephalic veins (without involving the SVC) also existed, another renal scan was performed, with injection of radiotracer into the contralateral arm. This showed a patent SVC and reasonably preserved renal perfusion consistent with acute tubular necrosis. Subsequently, left subclavian vein obstruction was identified. The graft function improved with conservative management for acute tubular necrosis. These findings illustrate the danger of considering only SVC obstruction when collateral flow patterns and focal hot spots in the liver are present.     

The clinical utility of radionuclide ventriculography in cardiac transplantation

To assess ventricular function in patients who have undergone cardiac transplantation, 247 radionuclide ventriculograms were performed on 94 patients. During the first three days after transplantation, 19% demonstrated left ventricular dysfunction and 41% showed isolated right ventricular dysfunction. In 95 cases, radionuclide ventriculography was performed within 24 hr of myocardial biopsy. A reduction in left ventricular ejection fraction to less than 50% was significantly more common with moderate-severe rejection than with mild rejection. In six instances in which there was discordance between ventriculography and biopsy, radionuclide ventriculography proved particularly useful: three cases showed severe left ventricular dysfunction despite only mild rejection by biopsy, and three cases with ventricular dysfunction from rejection were missed by the initial biopsy. Thus, radionuclide ventriculography can provide functional data in transplant patients that is complementary to myocardial biopsies since biopsy grade is a poor predictor of left ventricular function and biopsy can miss significant rejection.     

Cortex perfusion index: a sensitive detector of acute rejection crisis in transplanted kidneys

Damage to the renal cortical microcirculation, an early event in the course of acute rejection crisis (ARC), usually precedes measurable functional derangements in the transplanted kidney. Direct assessment of cortical blood flow by radionuclide renography may provide a sensitive and reliable index to the diagnosis of ARC, with particular regard to the differential diagnosis of ARC and ATN. Computer generated time-activity curves of global, cortical, and medullary renal blood flow were analyzed in 67 instances (35 patients) of renal allograft dysfunction and correlated with needle biopsy of these kidneys. No increase in cortex perfusion index (CPI), i.e., decrease in cortical perfusion, was found when the patients were suffering from ureteral obstruction or drug and viral nephropathy (mean perfusion index (PI) increase (8%). In contrast, a marked increase in CPI of 193% was noted in ARC. Global and medullary PI increased only 116%. As a result, global and medullary PI were capable of diagnosing ARC in only 73% and 55% of the cases, respectively, whereby cortex PI correctly diagnosed ARC in 94% of the cases. Selective analysis of cortical perfusion may thus enhance the accuracy of [99mTc]DTPA scans (radionuclide renograph) for the early detection of ARC and in differentiating ARC from nonimmunological causes of kidney allograft dysfunction.     

Importance of cytologic examination of urine in the diagnosis of renal transplant function disorders

BACKGROUND: This paper presents our experience with cytologic examination of urine in diagnosing renal allograft dysfunction. METHODS: The study group included 23 patients with renal allograft dysfunction, selected from 56 patients who underwent renal transplantation. Etiologic diagnosis was made according to the clinical picture, histological findings during allograft biopsy, and cytologic examination of urine. Urine sediment was obtained in cytocentrifuge and was air dried and stained with May Grunwald Giemsa. RESULTS: Out of 23 patients with allograft dysfunction in 18 (78.3%) patient it was caused by acute rejection, and in 5 (8.9%) patients by allograft infarction, cyclosporine nephrotoxicity, acute tubular necrosis and chronic nephropathy. In eighteen patients (78.3%) cytologic examination of urine was pathologic, while in 16 (70%) clinical and histology findings coincided with urine cytology findings. Out of 18 patients with acute allograft rejection in 15 patients cytologic examination of urine coincided with acute rejection. Out of 7 patients with expressed cyclosporine nephrotoxicity, in 5 cytologic examination of urine confirmed the cause of allograft dysfunction, as well as in one of 2 patients with acute tubular necrosis. Cytologic examination of urine indicated parenchymal damage in 2 patients with recurrent disease (membranoproliferative and focal sclerosing glomerulonephritis). In 4 of 5 patients suffering from chronic rejection in a year's monitoring period, urine sediment periodically consisted of lymphocytes, neutrophilic leucocytes, monocyte/macrophages, tubular cells and cylindres, without the predominance of any cell type. In 3 patients allograft dysfunction was caused by infective agents (bacteria, fungus, cytomegalovirus). CONCLUSION: Cytologic examination of urine might be an alternative to histological in diagnosing acute allograft rejection and acute tubular necrosis or nephrototoxicity. Also it might indicate parenchymal disease while the importance of urine cytology in chronic allograft nephropathy needs to be investigated further.     

Evaluation of allograft perfusion by radionuclide first-pass study in renal failure following renal transplantation

To assess the diagnostic value of indices measured on a first-pass curve, we performed 72 radionuclide renal first-pass studies (RFP) in 21 patients during the early weeks following renal allograft transplantation. The diagnosis was based on standard clinical and biochemical data and on fine needle aspiration biopsy (FNAB) of the transplant. Aortic and renal first-pass curves were filtered using a true low-pass filter and five different indices of renal perfusion were computed, using formulae from the literature. Statistical analysis performed on the aortic and renal indices indicated excellent reproducibility of the isotopic study. Although renal indices presented a rather large scatter, they all discriminated well between normal and rejection. Three indices have a particularly good diagnostic value. In the discrimination between rejection and Acute Tubular Necrosis (ATN), only one index gave satisfying results. The indices, however, indicate that there are probably ATN with an alternation of renal perfusion and rejection episodes where perfusion is almost intact. We conclude that radionuclide first-pass study allows accurate and reproducible quantitation of renal allograft perfusion. The measured parameters are helpful to followup the course of a post-transplantation renal failure episode and to gain more insight into renal ischemia following transplantation.     

Evaluation of allograft perfusion by radionuclide first-pass study in renal failure following renal transplantation

To assess the diagnostic value of indices measured on a first-pass curve, we performed 72 radionuclide renal first-pass studies (RFP) in 21 patients during the early weeks following renal allograft transplantation. The diagnosis was based on standard clinical and biochemical data and on fine needle aspiration biopsy (FNAB) of the transplant. Aortic and renal first-pass curves were filtered using a true low-pass filter and five different indices of renal perfusion were computed, using formulae from the literature. Statistical analysis performed on the aortic and renal indices indicated excellent reproducibility of the isotopic study. Although renal indices presented a rather large scatter, they all discriminated well between normal and rejection. Three indices have a particularly good diagnostic value. In the discrimination between rejection and Acute Tubular Necrosis (ATN), only one index gave satisfying results. The indices, however, indicate that there are probably ATN with an alternation of renal perfusion and rejection episodes where perfusion is almost intact. We conclude that radionuclide first-pass study allows accurate and reproducible quantitation of renal allograft perfusion. The measured parameters are helpful to followup the course of a post-transplantation renal failure episode and to gain more insight into renal ischemia following transplantation.     

Renographic indices for evaluation of changes in graft function

Radionuclide renal diagnostic studies play an important role in assessing renal allograft function, especially in the early post-transplant period. In the past two decades various quantitative parameters have been derived from the radionuclide renogram to evaluate changes in perfusion and/or function of the kidney allograft. In this review article we discuss the quantitative parameters that have been used to assess graft condition, with emphasis on the early postoperative period. These quantitative methods are divided into parameters used for assessing renal graft perfusion and parameters used for evaluating parenchymal function. The blood flow in renal transplants can be quantified (a) by measuring the rate of activity appearance in the kidney graft, (b) by calculating the ratio of the integral activity under the transplanted kidney and arterial curves and (c) by calculating the renal vascular transit time. In this article we review a number of parenchymal uptake and excretion indices, such as the accumulation index, the graft uptake capacity at 2 and 10 min, the excretion index and the elimination index. The literature on these parameters shows that they have some practical disadvantages. In addition, values suffer from significant overlap when various graft pathologies coexist. A retrospective study was designed in our institution to evaluate the clinical usefulness of some of the frequently used previously published methods in which the graft function is quantitatively assessed in the early post-transplant period. The quantitative parameters studied which were reasonably reproducible in our hands included: global perfusion index (GPI), cortical perfusion index (CPI), vascular transit time, and the parenchymal parameters uptake capacity at 2 min (UC₂) and elimination index (K_3/20). The patient population in this study consisted of 43 patients with 157 technetium-99m mercaptylacetyltriglycine renograms. The perfusion indices GPI and CPI did not allow differentiation of the acute tubular necrosis (ATN) group from the acute rejection (AR) group; however, they were of value in monitoring the improvement in the condition of the graft dysfunction in both the AR and ATN groups. As for the parenchymal parameters, both UC₂ and K_3/20 were able to differentiate stable graft function (SGF) versus AR and ATN groups but were unable to separate AR from ATN dysfunction. The ability of these parenchymal parameters to detect improvement in the graft function was poor and statistically non-significant. From the literature data and our own findings it is concluded that radionuclide scintigraphy of renal transplants has assumed an important role, especially if performed serially, in monitoring graft function in the post-transplant period. Many quantitative parameters have been derived from the radionuclide renogram to evaluate changes in perfusion and/or function of the kidney allograft. It appears that these quantitative numerical values are unable to differentiate unequivocally between grafts with ATN and AR cases. The real value of these parameters lies in the follow-up of the dysfunction processes, which helps the clinician to determine the appropriate therapeutic regimen.     

Assessment of renal allograft pathology by scintigraphic and ultrasound index-markers

The efficacies of two scintigraphic and two sonographic techniques and resultant index values, as markers of renal allograft pathology, were assessed. Index values of 183 combined scintigraphic and sonographic examinations in 47 graft recipients were compared to the pathological diagnosis of transplant biopsies and subsequent clinical outcome. All recipients were studied with baseline imaging techniques postoperatively, again when indicated by predefined clinical criteria, and prior to graft biopsy. The scintigraphic technique involved the calculation of indices of thrombotic activity and cortical graft perfusion. Ultrasound involved determination of the Doppler resistance index of Pourcelot and estimations of graft volume from real time images. A decreased cortical perfusion index was, overall, the most sensitive index of acute or chronic graft pathology, but it lacked specificity. Increased thrombotic and resistance indices were 96% and 86% sensitive for acute vascular rejection and were 82% and 76% specific. Jointly increased thrombotic and resistance indices improved the specificity for acute vascular rejection to 98%. An increase in graft volume of more than 50% over stable values was 100% sensitive and 92% specific for acute interstitial rejection, and 95% specific when paired with a normal thrombotic index. A marked increase in the thrombotic index was 100% sensitive for cyclosporine-induced thrombotic microangiopathy, but only 49% specific. The specificity of a markedly increased thrombotic index for thrombotic microangiopathy improved to 93% when the Doppler resistance index remained normal or was only marginally elevated. None of the scintigraphic or ultrasound indices were helpful for the diagnosis of acute tubular necrosis, chronic rejection, recurrent glomerulopathy, or graft infection.     

Duplex Doppler evaluation of renal allograft dysfunction: Doppler signal quantitation and pathologic correlation

The value of quantitative duplex Doppler sonography in discriminating the different possible causes of renal transplant dysfunction was prospectively studied in 60 patients during 65 episodes of renal function impairment. Final diagnosis at histology was acute rejection (n: 30), acute tubular necrosis (n: 4), cyclosporin nephrotoxicity (n: 16) and chronic rejection (n: 15). Duplex sonography was done the day a percutaneous biopsy was taken and before any therapy was started. Arterial Doppler signals obtained from the segmental, interlobar and arcuate arteries were both morphologically and quantitatively analysed. For quantitative analysis we used the resistive index as proposed by Pourcelot on the one hand, and introduced a variant resistive index on the other hand. Morphological analysis yielded no discriminative value. Comparing both quantitative methods--the resistive index of Pourcelot and the variant resistive index--clearly higher specificities--71% using the variant resistive index, 28% using the resistive index of Pourcelot--for excluding acute rejection from the other possible causes of renal function impairment could be achieved. A nephrectomy was done on 7 patients with severe transplant dysfunction. Microangiographies performed on these nephrectomy specimens were correlated with previous Doppler studies and with histology.     

Differentiation between renal allograft rejection and acute tubular necrosis by renal scan.

The usefulness of the renal scan in diagnosing technical complications in the transplant patient is well established. However, the ability of the renal scan to differentiate between acute rejection and acute tubular necrosis has remained uncertain. We have evaluated the effectiveness of the 99mTc DTPA computer-derived time-activity curve of renal cortical perfusion, as well as data obtained from scintillation camera images, in making such diagnoses. Fifteen patients with a clinical diagnosis of either acute rejection or acute tubular necrosis, or both, were studied retrospectively. Technetium scan diagnoses did not agree with the clinical assessment in nine of the patients. Thus selection of a course of treatment should not be based on data obtained from the scan alone.     

Duplex Doppler sonography of renal transplants: lack of sensitivity and specificity in establishing pathologic diagnosis

Recent reports have suggested the value of duplex Doppler sonography in the assessment of renal transplant function. Accurate diagnosis of acute rejection and its distinction from acute tubular necrosis and cyclosporine A toxicity have been claimed. We undertook a combined retrospective and prospective analysis of duplex Doppler examinations performed over a 2-year period to assess the value of such studies in evaluating renal allograft dysfunction. Seventy-seven sonographic examinations were performed on 77 renal transplants. A mean resistive index was calculated from Doppler measurements within main, segmental, and interlobar renal arteries by using the following ratio. peak systolic blood-flow velocity--minimum end-diastolic blood-flow velocity/peak systolic blood-flow velocity Forty-eight Doppler results were correlated with transplant biopsies and 29 with clinical course. Twenty-three episodes of acute allograft rejection were confirmed. When a resistive index of greater than or equal to 0.9 was used to indicate acute rejection, sonography had a sensitivity of only 9% and a specificity of 91% for this diagnosis. In one of eight cases of cyclosporine A toxicity and in three of six examples of acute tubular necrosis, the resistive index was greater than 0.9. In all six instances of chronic rejection, the resistive index was less than 0.84. None of eight patients with evidence of infection had a resistive index greater than 0.9. The resistive index range of 12 normally functioning allografts was 0.57-0.69. Correlation between the resistive index and the severity of arterial and arteriolar changes on biopsy was poor. An increased resistive index of renal transplant blood flow, as measured by duplex Doppler sonography, usually signals pathologic changes in an allograft. However, our data indicate that this test is not as sensitive or specific in identifying the cause of transplant dysfunction as has been suggested previously.     

99mTc-HM-PAO and 123I-amphetamine cerebral scintigraphy: a new, non invasive method in determination of brain death in children

Determination of brain death in infants and children is difficult and criteria used in adult brain death are regarded insufficient in pediatric cases. In comatose children, clinical signs of brain death and EEG monitoring may be of limited value, while intercerebral blood flow estimations can provide more direct information. Beside radionuclide bolus angiography of polar radiopharmaceuticals with sequential technique, two radioisotopes are introduced for static brain images. Injection of 123I-amphetamine or the 99mTc labelled lipophilic complex HM-PAO into the peripheral venous circulation enables more precise static imaging of parenchymatous brain perfusion and cellular function in contrast to conventional dynamic imaging because of retention in the intact brain parenchyma. Critical deficits or complete loss of cerebral perfusion can be readily documented. These studies are particularly helpful when clinical signs and EEG alone cannot establish the definite diagnosis of brain death. Their easy application and wide availability renders them especially useful in children.