Noninvasive radiological diagnosis of renal vein thrombosis in renal transplantation.

Thrombosis of the allograft renal vein is a rare complication of renal transplantation. Of 557 consecutive renal transplants performed between January 1, 1985 and November 30, 1989, 3 cases occurred for an over-all incidence of 0.4%. In 2 cases the diagnosis was made preoperatively with renal scintigraphy and duplex Doppler sonography. No graft was salvaged, despite timely diagnosis in 2 patients. We conclude that the diagnosis of renal vein thrombosis in the renal allograft recipient should be suspected clinically and by the radiographic findings of absent perfusion on renal scintigraphy, and the detection of an arterial signal, albeit abnormal, on duplex Doppler sonography. When diagnosed, nephrectomy appears to be the only treatment.     

Role of duplex Doppler sonography in diagnosis of acute allograft dysfunction—time to stop measuring the resistive index?

Measurement of vascular resistive index (RI) by duplex Doppler sonography (DDS) has been proposed as a non-invasive technique to detect the presence of acute rejection in renal allograft recipients. Our aim was to evaluate the clinical utility of this technique. From 107 patients we reviewed 159 biopsies that were performed from 1993 to 2001 for the investigation of acute allograft dysfunction. Histological findings were correlated with RI measurements by contemporaneously performed DDS. The majority of biopsies were carried out within the first 3 months post-transplantation (111/159). Sixty-eight biopsies showed acute rejection, 91 biopsies had findings other than rejection (acute tubular necrosis, CyA toxicity, recurrent GN). Using a threshold mean RI value of 0.9, the test had a specificity for acute rejection of 89%, but a sensitivity of just 6%. If the threshold was lowered the sensitivity rose, but specificity declined sharply. Average RI in the rejection group was not higher than in controls (0.73+/-0.11 vs 0.74+/-0.11, respectively). We conclude that measurement of RI by DDS does not contribute to the diagnosis of acute allograft dysfunction.     

Monitoring of renal allografts by duplex ultrasound

Abstract. Deterioration of renal transplant function due to rejection is accompanied by changes in renal blood flow that can be measured by duplex ultrasound (DU). In the present study, 60 transplanted patients were followed up. A total of 233 duplex examinations, 68 percutaneous biopsies, 44 renal scintigraphies, and 6 transplant nephrectomies were performed on these patients. Diagnoses were made on the basis of clinical and histological data. Renal perfusion was calculated by means of DU. In addition, the arterial Doppler signals were quantified using a pulsatility index (PI). Mean perfusion of normal renal allografts was 0. 47 1/min. A decrease in blood flow could be found in acute vascular and chronic rejection but not in acute cellular rejection. A lack of renal perfusion due to acute vascular rejection was observed in four patients. Mean PI, used as a parameter of DU, rose significantly in all forms of rejection, which could be diagnosed with a sensitivity of 93% and a specificity of 86%. Cyclosporin overdosage did not alter the Doppler flow shape.     

Monitoring of renal allografts by duplex ultrasound

Deterioration of renal transplant function due to rejection is accompanied by changes in renal blood flow that can be measured by duplex ultrasound (DU). In the present study, 60 transplanted patients were followed up. A total of 233 duplex examinations, 68 percutaneous biopsies, 44 renal scintigraphies, and 6 transplant nephrectomies were performed on these patients. Diagnoses were made on the basis of clinical and histological data. Renal perfusion was calculated by means of DU. In addition, the arterial Doppler signals were quantified using a pulsatility index (PI). Mean perfusion of normal renal allografts was 0.47 l/min. A decrease in blood flow could be found in acute vascular and chronic rejection but not in acute cellular rejection. A lack of renal perfusion due to acute vascular rejection was observed in four patients. Mean PI, used as a parameter of DU, rose significantly in all forms of rejection, which could be diagnosed with a sensitivity of 93% and a specificity of 86%. Cyclosporin overdosage did not alter the Doppler flow shape.     

Evaluation of canine renal transplants with pulsed Doppler duplex sonography

Preliminary studies of human renal transplants suggested that pulsed Doppler sonography may complement other studies of renal transplant dysfunction. To further evaluate the Doppler technique, 11 dogs who received renal transplants were examined a total of 50 times. No antirejection chemotherapy was used, and following rejection the kidneys were removed and examined histologically. The canine transplants underwent accelerated acute or hyperacute rejection. A pulsed Doppler index (PDI) was derived to quantitate patterns of renal blood flow and peripheral vascular resistance. Arterial Doppler signals were obtained from renal transplant branch vessels in vivo and the PDI consistently fell as rejection occurred. No arterial signals were obtained from one kidney which was subsequently proven to have arterial thrombosis. Pulsed Doppler analysis provides new information about renal transplant blood flow patterns and may demonstrate evidence of rejection and renal arterial occlusion.     

Renal duplex sonography: evaluation of clinical utility

With the exception of conventional angiography, no previously proposed screening test has the necessary sensitivity/specificity to guide further evaluation for correctable renovascular disease. Recently, renal duplex sonography has been suggested as a useful substitute in such screening for renovascular disease. This report analyzes our data collected over the past 10 months in evaluation of renal duplex sonography to examine its diagnostic value. The study population for renal duplex sonography validity analysis consisted of 74 consecutive patients who had 77 comparative renal duplex sonography and standard angiographic studies of the arterial anatomy to 148 kidneys. Renal duplex sonography results from six kidneys (4%) were considered inadequate for interpretation. This study population contained 26 patients (35%) with severe renal insufficiency (mean 3.6 mg/dl) and 67 hypertension (91%). Fourteen patients (19%) had 20 kidneys with multiple renal arteries. Bilateral disease was present in 22 of the 44 patients with significant renovascular disease. Renal duplex sonography correctly identified the presence of renovascular disease in 41 of 44 patients with angiographically proven lesions, and renovascular disease was not identified in any patient free of disease. When single renal arteries were present (122 kidneys), renal duplex sonography provided 93% sensitivity, 98% specificity, 98% positive predictive value, 94% negative predictive value, and an overall accuracy of 96%. These results were adversely affected when kidneys with multiple (polar) renal arteries were examined. Although the end diastolic ratio was inversely correlated with serum creatinine (r = -0.3073, p = 0.009), low end diastolic ratio in 35 patients submitted to renovascular reconstruction did not preclude beneficial blood pressure or renal function response. We conclude from this analysis that renal duplex sonography can be a valuable screening test in the search for correctable renovascular disease causing global renal ischemia and secondary renal insufficiency (ischemic nephropathy). Renal duplex sonography does not, however, exclude polar vessel renovascular disease causing hypertension alone nor does it predict hypertension or renal function response after correction of renovascular disease.     

A comparison of duplex Doppler ultrasonography and intrarenal manometry in the diagnosis of acute renal transplant rejection

Renal transplant rejection is frequently difficult to differentiate from other causes of renal dysfunction. This study examined the use of duplex Doppler ultrasound and intrarenal manometry in a consecutive series of 73 patients who underwent renal transplantation. Altogether 327 duplex scans were analyzed and, for each, a resistive index (RI) was calculated. A raised RI predicted rejection in patients with grafts that functioned immediately, but not in those that had delayed function. A rise in intrarenal pressure ( greater than or equal to 40 mmHg) indicated the presence of rejection in both groups. However, neither test had a sensitivity of more than 71% and this was not improved by combining the results of the two tests for each patient. Although both tests have a place in transplantation, renal biopsies may still be required to confirm rejection.     

Captopril renography and duplex Doppler sonography in the diagnosis of renovascular hypertension

Background. The purpose of this prospective study was to determine the clinical usefulness of captopril renal scintigraphy and duplex Doppler sonography in detecting haemodynamically significant renal artery stenosis (⩾60%) and predicting cure or improvement of hypertension following revascularisation. Methods. Twenty-eight patients with moderate or high index of clinical suspicion of renovascular hypertension underwent both captopril renal scintigraphy and duplex Doppler sonography before undergoing renal angiography. Patients with angiographically proved (⩾60%) RAS were treated by percutaneous transluminal renal angioplasty unless it was contraindicated. Results. The results of captopril renal scintigraphy and duplex Doppler sonography were compared by renal angiography of 45 renal arteries in 28 patients. Eleven renal arteries were excluded from further comparison, because no accurate Doppler signal could be obtained. The sensitivity and specificity of captopril renal scintigraphy in the identification of RAS (⩾60%) was 78% and 81% respectively. The sensitivity of duplex Doppler sonography was 83% and the specificity was 81%. Positive predictive values of both tests for blood pressure cure or improvement after PTRA were 86% for CRS and 85% for DDS. Conclusions. Captopril renal scintigraphy and duplex Doppler sonography are comparable tests for detection of patients with haemodynamically significant renal artery stenosis (⩾60%). Positive predictive values of both tests for cure or improvement of hypertension after percutaneous transluminal renal angioplasty are good and comparable.     

Sub‐clinical acute rejection detected using protocol biopsies in patients with delayed graft function

Abstract Acute rejection in renal transplants is difficult to diagnose when patients have delayed graft function (DGF) in the early post‐transplant period. In this study protocol, renal transplant biopsies were performed in an attempt to detect sub‐clinical acute rejection episodes. Eighty‐three patients were eligible for the study, of whom 33 had DGF. All had protocol renal transplant biopsies performed under ultrasound control at 7 days post‐transplant, and those with DGF had further biopsies weekly until the graft functioned. All histologically confirmed acute rejection episodes were treated. Sub‐clinical acute rejection was detected in 6/33 (18%) patients with DGF compared to 2/50 (4 %) in the other patients (P < 0.05). Borderline rejection was present in 4/33 (12 %) and 4/50 (8 %) patients, respectively. Because of the high detection rate of sub‐clinical acute rejection and the low morbidity of renal transplant biopsies, their use is recommended in patients with DGF.     

The presence of B-cell nodules does not necessarily portend a less favorable outcome to therapy in patients with acute cellular rejection of a renal allograft

The presence of B-cell nodules in kidney biopsies of patients undergoing acute renal allograft rejection has been reported to be associated with glucocorticoid resistance and a high risk of graft failure. In an attempt to corroborate this observation, biopsies of renal transplants that evidenced Banff grade I A acute rejection were examined for the presence of B- or T-cell nodules, the detection of which was correlated with the therapeutic response. Biopsies from 14 consecutive renal transplant recipients with a diagnosis of acute cellular rejection were examined for the presence of T (CD3-positive) or B (CD20-positive) cells by immunohistochemistry. All patients were biopsied because of a rise in serum creatinine. No biopsy showed evidence of acute humoral rejection. Immunofluorescence microscopy was negative for C4d deposition in peritubular capillaries. There were no neutrophils in the peritubular or glomerular capillaries. Five patients had T-cell nodules; four had B-cell nodules; three had both T- and B-cell nodules; two had no nodules. All biopsies contained CD3-positive cells in the tubules and in the interstitium. In all but one of the patients, episodes of acute rejection were treated with steroids (one received thymoglobulin). Furthermore two patients received mycophenolate mofetil and one, sirolimus. There were no significant differences among the groups in either the initial creatinine or the creatinine after therapy. The presence of B-cell nodules in renal allograft biopsies of patients experiencing acute cellular rejection did not portend a less favorable outcome.     

Predictive value of Doppler ultrasonography in renal transplantation

During a 17-month period, 268 Doppler sonography studies were performed on 46 consecutive renal transplant patients. There were 35 episodes of acute rejection in 10 patients, 8 episodes of delayed function and 47 episodes of high cyclosporine levels (greater than 800 ng/dl by TDX method) in 21 patients. Defining an abnormal resistive index (RI) as greater than 0.8 or a 20% increase above baseline, the test has a specificity of 99% and a sensitivity of 94% in the 1st month post-transplant and had an overall predictive value of 99%. Episodes of high cyclosporine levels ranging from 800 to 1650 ng/dl did not correlate with a high RI except in one circumstance with concurrent acute rejection. Within the 1st month post-transplant, only 1 false-negative study occurred. An additional 8 false-negative studies occurred beyond 1 month post-transplant. Patients with delayed function are separated into three groups based on the Doppler ultrasounds: Group I, patients with an accelerated acute rejection with high RI (N = 2); Group II, patients with true ischemic acute tubular necrosis with normal RI (N = 2); and Group III, patients with possible immunologically-mediated delayed function with intermediate RI between 0.6 and 0.8 (N = 4). Doppler ultrasound is a useful ancillary test to confirm the clinical suspicion of acute rejection. Since high cyclosporine levels do not cause an increase in RI, Doppler ultrasound may help to avoid confusion between acute rejection and cyclosporine toxicity. Additionally, this test may offer insight into the cause of early post-transplant renal dysfunction.     

Careful clinical monitoring in comparison to sequential Doppler sonography for the detection of acute rejection in the early phase after renal transplantation

Abstract Acute rejection is the most frequent cause of early graft failure. There is unanimity that Doppler sonography is a helpful method for the detection of complications after kidney transplantation. In the past, the indication for renal biopsy relied mainly on clinical assessment, although this assessment has not been standardised. Therefore, we conducted this prospective study to compare the value of sequential Doppler measurements with a standardised clinical rejection score, based on renal function, weight gain, graft swelling and tenderness. Fifty‐eight patients (37 males, 21 females, mean age 46 ± 12 years) after kidney transplantation were consecutively enrolled into the study. Doppler investigations were obtained within the first 24 h after transplantation, followed by an interval of 48‐72 h. At the same time, a clinical examination was scored by a transplant physician blinded to the Doppler results. Clinical score and Doppler results, both were referred to the histological results of renal biopsy. In 24 out of 58 patients 25 acute rejections occurred. In seven patients, acute rejection was superimposed on primary graft failure. The cut‐off levels for rejection were set at RI ≥ 0.80 and PI ≥ 1.70 based on receiver‐operator curves using data from 663 Doppler examinations. Sensitivity and specificity was 72 % for RI, and 72 % and 74 % for PI, respectively. The calculation of the intraindividual increase (ΔRI ≥ 3 %, ΔPI ≥ 10 %) did not improve these values. The clinical score revealed a sensitivity and specificity of 82% and 87 %, respectively. The combined analysis of Doppler indices and clinical score showed a sensitivity of 96 % with a specificity of 66%. Careful clinical monitoring alone using a clinical score is an appropriate procedure with which to decide about renal biopsy. Our data show that Doppler sonography should be performed within the first 24 h after transplantation to evaluate graft perfusion and baseline values. Afterwards, it should be used when clinical signs of rejection occur to underline the decision for renal biopsy even in borderline cases.     

Evaluation of cortical perfusion in renal transplants: application of quantified power Doppler ultrasonography

Perfusion of renal transplants may be altered by various pathological conditions. This study assessed cortical perfusion of renal transplants during acute rejection episodes using power Doppler quantification. Forty-eight renal transplant patients with clinical indications for biopsy were included in this study. Power Doppler ultrasonography (US) of these renal transplants was performed prior to biopsy. Power Doppler image intensity in the proximal outer cortex of renal transplants was quantified by image analysis software. The results of power Doppler quantification were compared with the clinical data and histological findings. Biopsies were classified into three groups based on Banff diagnostic categories: group 1 (no acute rejection; 26 patients), group 2 (acute cell-mediated rejection alone; 12 patients), and group 3 (acute antibody-mediated rejection with/or without acute cell-mediated rejection; 10 patients). The power Doppler intensity of the outer renal cortex was 1.98 +/- 1.50 dB for group 1, 1.38 +/- 0.86 dB for group 2, and 0.81 +/- 0.66 dB for group 3. Statistically, there was a significant difference between group 1 and group 3 (1.98 vs 0.81 dB, P = .01) but not between group 1 and group 2 (1.98 vs 1.38 dB, P = .34). In conclusion, the status of cortical perfusion of renal transplants can be determined noninvasively by quantified power Doppler US. Accordingly, acute antibody-mediated rejection is associated with significantly decreased cortical perfusion, which, we propose, is due to this distinct pathological process.     

Contribution of color and power Doppler sonography to the differential diagnosis of acute and chronic rejection, and tacrolimus nephrotoxicity in renal allografts

The aim of the present study was to differentiate acute rejection, chronic rejection, and tacrolimus nephrotoxicity with color and power Doppler imaging of renal transplants. One hundred examinations were obtained from 45 patients. Pulsatility and resistive indices were calculated from color Doppler images. The grade of renal vascularization was quantified using computer-assisted pixel analysis in a rectangular region-of-interest. The percentage of vessel-covered renal parenchyma (POV) was calculated using a histogram that discriminated renal vessels from renal parenchyma via power Doppler images. Furthermore, the distance from the most peripherally located vessels to the renal capsule (PVD) was measured. A reduced POV K 55 % proved to be the best discriminator when chronic rejection was suspected (sensitivity 79 %, specificity 87 %). Tacrolimus nephrotoxicity showed not only a moderate elevation of the Doppler signal but also an increased PVD L 3.9 mm and a normal POV. We conclude that the evaluation of renal vessels by power Doppler images improves diagnostic accuracy for patients with renal allografts. Received: 22 June 1998 Received after revision: 29 September 1998 Accepted: 12 October 1998     

A new approach for the screening of carotid lesions: a 'fast-track' method with the use of new generation hand-held ultrasound devices.

OBJECTIVES: We assessed the usefulness of fast-track neck sonography with a new-generation hand-held ultrasound scanner in the detection of > or =60% carotid stenosis. DESIGN: Patients with a past history of atherosclerotic disease or presence of risk factors were enrolled. All had fast-track carotid screening with a hand-held ultrasound scanner. METHODS: Initial assessment was performed with our quick imaging protocol. A second examiner performed a conventional complete carotid duplex as gold-standard. RESULTS: We enrolled 197 consecutive patients with a mean age of 67 years (range 35-94). A carotid stenosis >60% was detected in 13 cases (6%). The sensitivity, specificity, positive and negative predictive value of fast-track sonography was 100%, 64%, 17% and 100%, respectively. Concomitant power Doppler imaging during the fast-track method did not improve accuracy. CONCLUSIONS: The use of a fast-track method with a hand-held ultrasound device can reduce the number of unnecessary carotid Duplex and enhance the screening efficiency without missing significant carotid stenoses.     

Importance of Doppler sonography in urology

There have been major advances in Doppler technology over the last 5 years which are particularly useful in the field of urology. In the early 1980s the clinical significance of Doppler was limited to the diagnosis of testicular torsion and its use was primarily intraoperative. Today, however, new advances, i.e. pulsed Doppler, duplex sonography, and color-coded duplex sonography (angiodynography), have cleared the way for totally new approaches to vascular impotence, renal artery stenosis, renal artery embolus, intratumor flow measurement, and control of renal transplants. These new technical advances will be exemplified in typical pathological states.     

Renal transplant blood flow evaluation by ultrasonic duplex scanning

The transplant blood flow was measured renal transplantation by ultrasonic duplex scanner composed of pulsed Doppler flowmeter and real-time B-mode linear scanner in 32 patients. The blood flow information could be obtained from anywhere of interest within the renal transplant. Then blood flow in 3 regions including renal hilum, central echoes and renal parenchyma were measured. The parenchymal peripheral blood flow was not always similar to the hilar central blood flow. Parenchymal blood flow was the most correlated with graft function and decreased remarkably during acute rejection episode. This method enabled detection of occurrence of acute rejection in the course of post-cadaver transplant ATN. Prolongation of delta t (acceleration time) in Doppler spectrogram from parenchyma was also reliable evidence for the deterioration of graft function. Ultrasonic duplex scanning is a useful method in managing post-transplantation patients because intrarenal hemodynamics can be evaluated by this method.     

Improvement of renal function in pediatric heart transplant recipients treated with low-dose calcineurin inhibitor and mycophenolate mofetil

BACKGROUND: Renal dysfunction is a major complication in heart transplant recipients treated with calcineurin inhibitors. The goal of the study was to investigate the effect of a reduction of calcineurin inhibitor dosage with the concomitant introduction of mycophenolate mofetil on both renal function and cardiac allograft function. METHODS: Fourteen of 52 consecutive pediatric cardiac allograft recipients experienced a progressive decrease of renal function. A renal biopsy was performed before the dose of calcineurin inhibitors was reduced by 50% and azathioprine was replaced by mycophenolate mofetil. Renal function was evaluated by inulin clearance and maximal urinary osmolality before and yearly after the therapeutic changes. Acute rejection was monitored clinically, by echocardiography and endomyocardial biopsies. RESULTS: Inulin clearance in the fourteen children decreased from 84.2 mL/min/1.73 m at one year posttransplantation to 46.5+/-9.6 mL/min/1.73 m at the time of the change in immunosuppressive therapy. Significant renal lesions were observed in the renal biopsies performed before the change. At 1 year, inulin clearance had increased by 67%. In six patients who had a second determination 2 years after the switch, inulin clearance was not significantly different from the value at 1 year. There were three reversible acute rejection episodes in three patients. The incidence of rejection episodes was not different from a control group of patients whose treatment was not changed. CONCLUSION: The reduction of calcineurin inhibitor dosage and replacement of azathioprine by mycophenolate mofetil is a safe way to improve renal function in children with heart transplants and calcineurin inhibitor induced nephrotoxicity.     

Duplex Doppler sonography in patients with acute renal colic: Prospective study and literature review

PURPOSE: To determine the value of duplex Doppler sonography in the diagnosis of acute urinary obstruction. MATERIALS AND METHODS: In 46 healthy individuals and 42 patients with urinary obstruction confirmed by intravenous urography, 176 kidneys were examined with duplex Doppler sonography. The mean intra-arterial resistive index value and the difference of mean resistive index values between both kidneys were determined for each person. Resistive index and delta resistive index values were compared with urographic findings in the 42 patients. RESULTS: In the 46 healthy individuals, the mean resistive index and delta resistive index values were 0.59 +/- 0.05 and 0.03 +/- 0.01. In the 14 patients with complete urinary obstruction, these values were 0.70 +/- 0.06 and 0.09 +/- 0.02, whereas in the 28 patients with partial urinary obstruction, these values were 0.64 +/- 0.06 and 0.03 +/- 0.05. Urographic findings and duplex Doppler sonography were correlated in the 42 patients, with a resistive index = 0.65 and delta resistive index = 0.05 as discriminatory thresholds for obstruction. In patients with complete obstruction, the diagnostic sensitivity of these values was 64% and 100% with a specificity of 82% and 89%, respectively. In patients with partial obstruction, the sensitivity of these values was 54% and 46% with a specificity of 82% and 89%, with respect to the control group of healthy individuals. CONCLUSION: Delta resistive index is a very sensitive and specific parameter in the sonographic diagnosis of complete urinary obstruction but insensitive in partial urinary obstruction. Duplex Doppler sonography is recommended in cases where intravenous urography is contraindicated.     

彩色多普勒超声诊断早期移植肾急性排斥

目的探讨彩色多普勒超声图像数据分析在诊断早期移植肾急性排斥中的作用及临床价值.方法总结203例肾移植术后6～30d内行彩色多普勒超声检查,结合临床症状、生化检查并参照病理诊断,对二维灰阶图像、彩色血流图、血流频谱及阻力指数(RI)、搏动指数(PI)、收缩期与舒张期血流速度比(S/D)等参数进行回顾性分析.结果以彩色多普勒RI>0.78、PI>1.82、S/D>4.1为标准,结合彩色血流图及血流频谱形态,早期移植肾急性排斥正确诊断率可达85.7%.结论应用彩色多普勒超声诊断移植肾早期急性排斥并监测其功能恢复,具有快速、准确、无创等优点,可提早发现病情变化并指导治疗,提高移植肾存活率.