Transplant Artery Research Articles

Doppler Ultrasound for Detection of Renal Transplant Artery Stenosis—Threshold Peak Systolic Velocity Needs to be Higher in a Low-risk or Surveillance Population

Abstract AIMS: To establish the ideal threshold arterial velocity for the diagnosis of renal transplant artery stenosis in a surveillance population with a low pre-test probability of stenosis. METHODS: Retrospective review of Doppler ultrasound, angiographic and clinical outcome data of patients transplanted over a 3-year period. Data used to calculate sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) for various threshold peak systolic velocity values. RESULTS: Of 144 patients transplanted, full data were available in 117 cases. Five cases had renal transplant artery stenosis—incidence 4.2% [stenosis identified at a mean of 6.5 months (range 2–10 months)]. All five cases had a significant arterial pressure gradient across the narrowing and underwent angioplasty. Threshold peak systolic velocity of ≥2.5 m/s is not ideal [specificity=79% (CI 65–82%), PPV=18% (CI 6–32%), NPV=100% (CI 94–100%)], subjecting many patients to unnecessary angiography—8/117 (6%) in our population. Comparable values if the threshold is set at ≥3.0 m/s are 93% (CI 77–96%), 33% (CI 7–44%) and 99% (CI 93–100%), respectively. The clinical outcome of all patients was satisfactory, with no unexplained graft failures or loss. CONCLUSIONS: In a surveillance population with a low pre-test probability of stenosis, absolute renal artery velocity ≥2.5 m/s is a limited surrogate marker for significant renal artery stenosis. The false-positive rate is high, and ≥3.0 m/s is a better choice which will halve the number of patients enduring unnecessary angiography. Close clinical follow-up of patients in the 2.5–3.0 m/s range, with repeat Doppler ultrasound if necessary, will identify the test false-negatives.

Imaging in renal transplantation.

Renal transplantation is the best treatment option for chronic renal failure, with marked improvement in social activity, work, and family life. In addition to these obvious improvements, it is an extremely cost-effective procedure when successful. Ultrasonography plays a major role in the imaging of these patients, and ultrasound (including color Doppler) is helpful to the transplant physician in detecting graft dysfunction and peritransplant collections, some of which may be drained under ultrasound guidance. It is also helpful in the diagnosis of chronic vascular complications including transplant artery stenosis and arteriovenous fistula. It has no specific application in the diagnosis of chronic rejection.

Multiple Arteries in Live Donor Renal Transplantation: Surgical Aspects and Outcomes

This retrospective study describes the surgical techniques and outcomes of live donor renal allografts with multiple arteries. Between 1976 and 2000, 1,200 consecutive live donor renal transplants were done, including 1,087 with single (group 1) and 113 with multiple (group 2) arteries. Intracorporeal in situ anastomotic techniques were used for 94 grafts with multiple arteries, while ex vivo techniques were used for 19. During in situ surgery each one of the multiple arteries was anastomosed separately to an individual artery. In ex vivo surgery 2 or more arteries were joined together on the bench to form a common stem, which was then anastomosed to an iliac artery or the aorta. Patient and graft survival were comparable in groups 1 and 2. The 2 groups were comparable regarding complications, including arterial bleeding, hematoma, renal artery stenosis, acute rejection, new onset hypertension, acute tubular necrosis and urological complications. Mean serum creatinine +/- SD at 1 year was 1.4 +/- 0.5 and 1.5 +/- 0.6 mg./dl., and at 5 years it was 1.8 +/- 1 and 2.1 +/- 1.4 mg./dl. for the 2 groups, respectively. The difference was only significant at 1 year (p = 0.02). Graft and patient survival, and the incidence of the described complications were comparable for the ex vivo bench anastomotic techniques and intracorporeal in situ techniques in the group with multiple renal arteries. The use of multiple arteries in renal allografts does not adversely affect patient or graft survival. It is not associated with an increased rate of complications except for significantly higher mean serum creatinine at 1 year. Extracorporeal bench surgery was as effective as intracorporeal surgery for the anastomosis of multiple renal arteries with no increase in the incidence of relevant complications.

Histopathological study of renal transplant artery stenosis: role of rejection and cold ischaemia time in the pathogenesis of intimal hyperplasia in an arterial allograft.

Intimal hyperplasia of renal allograft arteries is a cause of hypertension and graft loss and the predisposing factors are poorly understood. We performed a histopathological study focusing on cold ischaemia time and immunological factors and their effect on the donor artery. Primary renal artery branches were obtained from patients undergoing transplant nephrectomy for chronic rejection. Non-transplant patients undergoing nephrectomy served as controls. Clinical information including immunosuppression and rejection episodes, cold ischaemia time and graft survival were collected from the patients' charts. Collagen, smooth muscle cells, T cells, macrophages, and neutrophils were quantified using immunohistochemistry. The intima to media ratio was also calculated using imaging software. Statistical analysis was performed using linear regression and the Mann-Whitney test with P < 0.05 significant. Nine transplant patients and five controls were included. All transplant patients received maximum immunosuppression according to clinical standards. The median number of acute rejection episodes was 1 (range 0-5). Cold ischaemia time was 24.3 +/- 9.6 h (mean +/- SD). Mean allograft longeviy was 87.4 +/- 72.9 months (mean +/- SD). The intima/media ratio in the transplant group was higher as compared with the control (P = 0.002). The same was true for intima collagen content (P = 0.001) and intima smooth muscle content (P = 0.036). Cold ischaemia time was 19.6 +/- 11.1 h (mean +/- SD) and did not correlate with intima/media ratio. Also the number of rejection episodes did not correlate with the intima/media ratio. Intimal hyperplasia in the allograft artery has a multifactorial aetiology. We were not able to establish an association between intimal hyperplasia and acute rejection episodes or length of cold ischaemia time. It appears that immunosuppression does not prevent the development of intimal hyperplasia.

Influence of acute selective endothelin-receptor-A blockade on renal hemodynamics in a rat model of chronic allograft rejection.

We have recently demonstrated up-regulation of renal endothelin (ET) synthesis in a rat model of chronic renal allograft rejection. Treatment with a selective ET-A receptor antagonist improved survival and reduced functional and morphological kidney damage. However, the underlying mechanisms have not yet been elucidated, as ET exhibits both hemodynamic and inflammatory properties. Therefore, in the present study we investigated acute hemodynamic effects of the selective ET-A receptor antagonist LU 302146 (LU) on chronic renal allograft rejection in rats. Experiments were performed in the Fisher-to-Lewis model of chronic renal allograft rejection. Lewis-to-Lewis isografts served as controls. After 2, 12, and 24 weeks, hemodynamic measurements were performed on anesthetized animals. Measurement of mean arterial pressure (MAP) was performed via a catheter in the femoral artery. Renal blood flow (RBF) was measured by an ultrasonic flow probe placed around the renal transplant artery. Medulla blood flow (MBF) and cortex blood flow (CBF) were determined with laser Doppler probes. Hemodynamic response upon intravenous bolus injection of LU (50 mg/kg) was investigated. The application of LU was followed by a decline in MAP that reached statistical significance only in isografts (ISOs) after 12 weeks and allografts (ALLOs) after 24 weeks. RBF slightly decreased in all groups; however, without reaching statistical significance. MBF showed a small increase in ALLO12 and ALLO24 whereas CBF slightly decreased in all groups. Acute ET-A receptor blockade does not induce important hemodynamic effects in kidneys undergoing chronic rejection. The lack of response to ET-A receptor blockade suggests that the beneficial effect of ET receptor antagonists in this model is likely to be due to improvement of renal morphology.

RAS blockade in experimental renal transplantation. Benefits and limitations.

In renal transplantation, chronic renal transplant failure (CRTF) is the principal cause of late graft loss. Both immunological and non-immunological factors play a role in the pathogenesis of CRTF. However, CRTF is unresponsive to immunosuppressive therapy. In several kidney diseases, inhibition of the renin-angiotensin system (RAS) has shown to reduce the rate of progression of renal disease more effectively than conventional antihypertensive drugs. Therefore, RAS blockade may be of benefit in the treatment of CRTF. Several short-term studies in human renal transplant recipients showed that RAS blockade had a beneficial effect on renal transplant function, blood pressure and proteinuria. Despite these benefits physicians remain reluctant to use ACE inhibition in these recipients, because of fear of functional decrease in renal perfusion, especially in the setting of renal transplant artery stenosis. To study the long-term effects of RAS blockade we used the established Fisher to Lewis (F-L) model for CRTF, which mirrors the progressive changes seen in humans. Studies in our lab and by others showed that RAS blockade in the F-L model prevents proteinuria, glomerulosclerosis and hypertension. However, when treated for 34 weeks with RAS blockade, renal arteries developed severe intimal hyperplasia. This effect was specific for Fisher rats. Syngrafted Fisher rats treated with ACE inhibition developed intimal hyperplasia, but allografting significantly aggravated it. Fisher rats have a four times higher renal ACE activity, compared with the Lewis rat. This is comparable to the human DD/II genotype differences in ACE activity. Renal transplant patients with the DD genotype may be more vulnerable for vascular changes when treated with RAS blockade.

Anesthetic Management of Combined Lung Transplant and Coronary Artery Bypass Surgery without Cardiopulmonary Bypass

Anesthetic Management of Combined Lung Transplant and Coronary Artery Bypass Surgery without Cardiopulmonary Bypass

Histomorphologische Strukturveränderungen von Kopf-Hals-Gefäßen nach prä- oder postoperativer Radiotherapie

Patients with squamous cell carcinomas of the oral cavity are being increasingly treated by multimodal interdisciplinary regimes using a combination of surgery, chemo- and radiotherapy. Inflammatory alterations of the vascular endothelium following preoperative radiotherapy frequently cause healing delays of free flaps in the irradiated graft bed. The aim of the study was to investigate quantitative and qualitative changes of irradiated neck recipient vessels and transplant vessels used for microsurgical anastomoses in free flaps in patients undergoing preoperative radiotherapy or radiochemotherapy. In 348 patients (October 1995-March 2002) receiving primarly or secondary 356 microvascular hard- and soft tissue reconstruction, a total of 209 vessels were obtained from neck recipient vessels and transplant vessels during anastomosis. Three groups were analysed: group 1 (27 patients) treated with no radiotherapy or chemotherapy; group 2 (29 patients) treated with preoperative irradiation (40-50 Gy) and chemotherapy (800 mg/m2/day 5-FU and 20 mg/m2/day cisplatin) 1.5 months prior to surgery; group 3 (20 patients) treated with radiotherapy (60-70 Gy) (median interval 78.7 months; IQR: 31.3 months) prior to surgery. From each of the 209 vessel specimens, 3 sections were investigated histomorphometrically, qualitatively and quantitatively (ratio media area/total vessel area) by NIH-Image-digitized measurements. To evaluate these changes as a function of age, radiation dose and chemotherapy, a statistical analysis was performed using an analysis of covariance and chi 2 tests (p > 0.05, SPSS V10). In group 3, qualitative changes (intima dehiscence, hyalinosis) were found in recipient arteries significantly more frequently than in groups 1 and 2. For group 3 recipient arteries, histomorphometry revealed a significant decrease in the ratio media area/total vessel area (median 0.51, IQR 0.10) in comparison with groups 1 (p = 0.02) (median 0.61, IQR 0.29) and 2 (p = 0.046) (median 0.58, IQR 0.19). No significant difference was found between the vessels of groups 1 and 2 (p = 0.48). There were no significant differences in transplant arteries and recipient or transplant veins between the groups. Age and chemotherapy did not appear to have a significant influence on vessel changes in this study (p > 0.05). Following irradiation with 60-70 Gy, significant qualitative and quantitative histological changes to the recipient arteries, but not to the recipient veins, could be observed. In contrast, irradiation at a dose of 40-50 Gy and chemotherapy given at a median interval of 1.5 months prior to operation did not lead to significant histological changes to the recipient vessels.

Acute thrombosis of renal transplant artery: graft salvage by means of intra-arterial fibrinolysis.

Arterial thrombosis in a transplanted kidney is a serious complication that usually leads to graft loss. The purpose of our study was to evaluate intra-arterial fibrinolysis as a treatment of acute renal transplant artery thrombosis and to determine the maximum period of occlusion allowing a reasonable chance of graft salvage. Four patients underwent intra-arterial fibrinolysis for acute transplant artery thrombosis. Transplantations had been performed 29 days to 10 years before the fibrinolysis. Fibrinolysis was carried out by using recombitant tissue plasminogen activator (n=1) or urokinase (n=3). In one patient, anuric for 13 hr at admittance, fibrinolysis could not revascularize the graft artery. In a second patient, anuric for 48 hr at admittance, fibrinolysis did revascularize the graft artery, but dialysis could not be discontinued. In the two remaining patients, anuric for 19 and 20 hr at admittance, the graft artery was successfully revascularized and dialysis could be discontinued 1 week later. One of these two patients returned to dialysis 71 months later because of chronic rejection. Thirty-four months after the acute episode, the remaining patient had a patent artery and did not require dialysis. Fibrinolysis seems an efficient treatment that may save transplants after up to 24 hr of the arterial occlusion.

Renal transplant evaluation with MR angiography and MR imaging.

Magnetic resonance (MR) angiography is a widely used, noninvasive tool for evaluating the aorta and its branches. It is particularly useful in renal transplant recipients because it provides anatomic detail of the transplant artery without nephrotoxic effects. Volume rendering is underutilized in MR angiography, but this technique affords high-quality three-dimensional MR angiograms, especially in cases of tortuous or complex vascular anatomy. An imaging protocol was developed that includes gadolinium-enhanced MR angiography of the transplant renal artery with volume rendering and multiplanar reformation postprocessing techniques. Axial T2-weighted and contrast material-enhanced T1-weighted MR images are also obtained to examine the renal parenchyma itself and to evaluate for hydronephrosis or peritransplant fluid collections. This imaging protocol allows rapid global assessment of the renal transplant arterial system, renal parenchyma, and peritransplant region. It can also help detect or exclude many of the various causes of renal transplant dysfunction (eg, stenosis or occlusion of a transplant vessel, peritransplant fluid collections, ureteral obstruction). Conventional angiography can thus be avoided in patients with normal findings and reserved for those with MR angiographic evidence of stenosis.

Long-term follow up of renal transplant artery stenosis by doppler

Long-term follow up of renal transplant artery stenosis by doppler

Duplex doppler follow-up of renal transplant artery stenosis in children

Duplex doppler follow-up of renal transplant artery stenosis in children

Hypertension after renal transplantation.

With current immunosuppression, elevated blood pressure is found in almost 90% of renal graft recipients. Major causes of this are impairment of renal function (secondary to chronic allograft nephropathy or less frequently recurrence of primary renal disease), the use of calcineurin inhibitors as immunosuppressants, uncontrolled renin secretion by the shrunken kidneys of the recipient, stenosing lesions of the transplant artery (or the upstream arteries of the recipient), polycythemia, and genetic predisposition to hypertension of the graft donor. Even minor degrees of blood pressure elevation have a significant impact on survival of the recipient and on graft survival, presumably by amplifying vascular injury to the graft. In this respect, elevation of systolic blood pressure and an abnormal circadian blood pressure profile are of particular relevance. In contrast to previous opinion, angiotensin converting enzyme inhibitors are indicated in treatment, but given the causal role of sodium retention and graft vasoconstriction, diuretics and calcium channel blockers remain mainstays of antihypertensive treatment in the renal allograft recipient.

Sequential anastomosis of accessory renal artery to inferior epigastric artery in the management of multiple arteries in live related renal transplantation: a critical appraisal.

In live related renal transplant program, management of multiple renal arteries (MRA) is technically demanding and used to be considered a relative contraindication because of increased risk of vascular and urologic complications. We present a retrospective analysis of the outcome of grafts with MRA and suggest certain guidelines. Of the 680 live related kidney transplantations done, 53 allografts had MRA. Cases were grouped according to the reconstruction technique: group A, MRA reconstructed ex vivo into a single renal artery (n=27); group B, MRA with multiple anastomoses in vivo (n =13); group C, MRA with sequential revascularization using inferior epigastric artery (n=11). We compared serum creatinine, acute tubular necrosis, rejection rates and the rewarm ischemia time between the three groups. Overall patient survival and graft survival were excellent (100 and 96%). Mean serum creatinine at 1 yr did not differ significantly between the three groups. Rewarm ischemia time was significantly less in group C (p<0.01). Incidence of acute tubular necrosis and rejection episodes was also less in group C although the difference was statistically significant only between group C and group B. We conclude that allografts with MRA can be used successfully in a live related renal transplantation program. Bench reconstruction should be done whenever possible. For reconstruction of an accessory vessel, inferior epigastric artery with sequential revascularization is recommended.

Authors’ reply:

Authors’ reply:

Double renal arteries in living-related kidney transplantation

Double renal arteries in living-related kidney transplantation

Anwendung der virtuellen Realität für MRA-Daten komplexer Gefäßstrukturen

During the last years because of the progress in magnetic resonance imaging (MRI) magnetic resonance angiography (MRA) has become a serious alternative to conventional X-ray angiography. The potential of MRA in combination with methods for three-dimensional reconstruction will be presented and different methods for image post-processing are discussed based on a number of cases. The examinations were performed on a clinical 1.5 T magnetic resonance tomograph (Siemens Vision, Erlangen) using conventional MR angiography sequences. The different options of post-processing were carried out online on the console and offline using dedicated workstations (Siemens Virtuoso and CHILI). Complex post-processing procedures are applied to different areas like pulmonary vasculature, thoracic aorta, abdominal aorta, and renal transplant arteries. Different diagnostic values can be seen for the variety of three-dimensional reconstruction methods. According to our experience volume rendering has been selected as the method of choice due to the time needed for reconstruction and the information content of the resulting image.

Inferior epigastric artery for revascularization of lower polar arteries in renal transplantation

Inferior epigastric artery for revascularization of lower polar arteries in renal transplantation

Extra-renal pseudoaneurysm: An uncommon complication following renal transplantation

Vascular complications are reported in a significant proportion of patients following renal transplantation and are a contributory cause of graft dysfunction. Of these, pseudoaneurysm formation is one of the least common. We present three patients in whom extra-renal transplant artery pseduoaneurysms arising from the surgical anastomosis between the external iliac and renal transplant artery were initially diagnosed with colour Doppler ultrasound, and outline their subsequent management.

The impact of recurrent glomerulonephritis on graft survival in recipients of human histocompatibility leucocyte antigen-identical living related donor grafts.

Graft loss due to rejection is uncommon after human histocompatibility leukocyte antigen-identical living related donor (LRD) transplantation, resulting in an excellent long-term graft survival. Data on the impact of recurrence of the original disease on graft survival after LRD transplantation are scarce. We have studied the influence of recurrent glomerulonephritis in adult recipients of a human histocompatibility leukocyte antigen-identical LRD graft transplanted in our center in the period from 1968 to 1996. To that end, the data of 33 patients with proven or suspected primary glomerulonephritis and 27 patients with nonglomerular diseases were analyzed. The patient survival was similar in both groups at 5, 10, and 20 years. The functional graft survival, i.e., graft survival after censoring for death, was, however, significantly worse for patients with glomerulonephritis as underlying disease (P<0.01). At 5 years graft survival was 100% vs. 88%, at 10 years 100% vs. 70%, and at 20 years 100% vs. 63%, respectively. Thus none of the patients with nonglomerular diseases lost a graft, whereas eight grafts were lost in the group of patients with glomerulonephritis. The main cause of graft loss in this patient group was recurrent glomerulonephritis (n=5), whereas chronic vascular rejection caused graft loss in two patients and occlusion of a transplant artery was the cause in one. A clinically significant proteinuria was detected in six more patients in the glomerulonephritis group: a recurrent glomerulonephritis was diagnosed in four patients and in two patients there was no biopsy. The cumulative incidence of recurrence was as high as 45% at 12 years after transplantation. Recipients of a human histocompatibility leukocyte antigen-identical LRD kidney have a good prognosis with respect to graft survival. After censoring for death, recurrent glomerulonephritis is the main cause of graft failure in these patients and the impact of recurrent disease on graft survival will become even more prominent with longer follow-up.