Peripheral vascular disease and renal transplant artery stenosis: a reappraisal of transplant renovascular disease

Endovascular Treatment for Transplant Renal Artery Stenosis: 10 Years' Experience from a Single Center

INTRODUCTION

Transplant renal artery stenosis (TRAS) is a common post-renal transplant complication. Although endovascular treatment is widely used to treat TRAS, previous research has been limited by small sample sizes. This article aimed to present the clinical outcomes of endovascular treatment for TRAS in a large sample.

METHODS

Between January 2010 and December 2019, this study included patients with TRAS who were admitted to our center. All patients' clinical symptoms, comorbidities, imaging data, treatment, and follow-up results were reviewed retrospectively.

RESULTS

Seventy two patients participated in this study. The median time between renal transplantation and TRAS was 5.25 months. Out of 72 patients, 55 (76.4%) received balloon dilatation in conjunction with stent deployment, 10 (13.9%) received drug-coated balloon dilatation alone, and 7 (9.7%) received balloon dilatation alone. The median follow-up period was 27 months. Primary patency rates were 100%, 81.8%, 74.5%, 64.6%, and 61.8% at 1, 3, 6, 12, and 24 months. A total of 23 patients were found to have restenosis during follow-up, with 6 (26.1%) requiring reintervention and none remaining restenosis after the second treatment. In the subgroup analysis of the three types of stenosis, patients with transplant renal stenosis at the anastomosis had a significantly higher rate of primary patency. Between endovascular treatments, the primary patency rate, postoperative creatinine clearance, and mean systolic blood pressure did not differ significantly.

CONCLUSION

Endovascular treatment resulted in favorable short-term patency as well as effective relief of renal dysfunction and renal hypertension in TRAS patients.

Transplant Renal Artery Stenosis Revascularization: Common Distal External Iliac Bypass

Stenosis proximal to transplant renal artery anastomoses are complications leading to allograft dysfunction. This study was aimed to evaluate a novel surgical approach to renal allograft revascularization, taking into consideration the length of time elapsed since transplantation. We describe an arterial bypass using a polytetrafluoroethylene (PTFE) graft from the common iliac artery (proximal to the renal artery implantation) to the external iliac artery (distal to the renal artery implantation) that allows the adequate revascularization of both the transplant kidney, as well as the lower extremity. This technique provides several advantages when compared with previously described procedures to revascularize a transplanted kidney with an iliac artery stenosis proximal to the allograft implantation site. Benefits of this technique include (1) no need to repair the stenosis, (2) no need to take down and redo the arterial anastomosis, (3) no need to perform a dissection around the renal hilum of the transplanted kidney, (4) no requirement to address the anastomosis transfer, and (5) no need to perfuse the kidney with preservation fluid at the time of repair and/or (6) avoidance of potential injury to the renal parenchyma and/or hilum during dissections. Adequate perfusion of the organ, as well as of the lower extremity was verified by serial Doppler duplex ultrasound evaluations. Hence, we describe a novel revascularization technique in instances of kidney transplant and lower extremity ischemia.

Malignant hypertension secondary to iliac artery stenosis after kidney transplantation: a case report

Iliac artery stenosis is a rare complication after renal transplantation. This complication affects elderly patients and related to atheromatous disease. It mimics the same clinical presentation as a transplant renal artery stenosis or renal artery stenosis. This entity is can be responsible for serious complications such as renal dysfunction, malignant hypertension and acute pulmonary oedema. We present in this paper the case of a 51-year-old patient, who benefited 7 years early of renal transplantation, with a good initial result, and who was admitted actually for malignant hypertension and renal function impairment due to an iliac artery stenosis proximal to the renal transplant and who was treated with a stenting angioplasty of the external iliac artery with a mixed outcome. Our case highlights the importance of the early diagnosis and treatment of such complications to avoid definitive renal failure and permanent hypertension.

Transplant Ureteral Stenosis after Renal Transplantation: Risk Factor Analysis

INTRODUCTION

The results of kidney transplants have improved dramatically in recent years, leading to reduced morbidity and mortality. Despite continuous improvements, urological complications occur at a rate of 2.6%-15%. Ureteral stenosis of graft ureters is the most common complication, with a probability of 0.5%-6.3%. This study aimed to determine the incidence of ureteral stenosis after kidney transplantation and identify risk factors that distinguish transplant patients with and without ureteral stenosis.

METHODS

This study retrospectively analyzed patients who had undergone kidney transplantation at the Department of Urology of the Friedrich-Alexander University Erlangen-Nuremberg between 2001 and 2015. Forty-seven patients developed ureteral stenosis during the operation. Most of the ureteral stenosis cases occurred in the first 4 months after transplantation. Kaplan-Meier analysis and the log-rank test were used to calculate the cumulative risk, and the Mann-Whitney U test was used nonparametrically. The significance level was set at p < 0.05.

RESULTS

Statistical analysis showed that residual diuresis (p = 0.008), cold ischemia time (CIT) (p = 0.040), the body mass index (p = 0.027), and donor serum creatinine value (p = 0.039) showed a significantly different distribution between recipients with or without ureteral stenosis after kidney transplantation. In multivariate Cox's regression modeling, residual diuresis and the donor serum creatinine level were identified as the only independent predictors of patients' stenosis-free survival.

CONCLUSION

Urological complications not diagnosed and treated in time endanger the success of kidney transplantation. After evaluating the kidney transplantation data of the patients at the Transplant Center Erlangen-Nuremberg from 2001 to 2015, residual diuresis, CIT, the body mass index, and donor serum creatinine value were found to influence the development of ureteral stenosis.

Role of hypertension in kidney transplant recipients

Cardiovascular events are one of the leading causes of mortality in kidney transplant recipients. Hypertension is the most common comorbidity accompanying chronic kidney disease, with prevalence remaining as high as 90% even after kidney transplantation. It is often poorly controlled. Abnormal blood pressure profiles, such as masked or white-coat hypertension, are also extremely common in these patients. The pathophysiology of blood pressure elevation in kidney transplant recipients is complex and includes transplantation-specific risk factors, which are added to the traditional or chronic kidney disease-related factors. Despite these observations, hypertension management has been an under-researched area in kidney transplantation. Thus, relevant evidence derives either from studies in the general population or from small trials in kidney transplant recipients. Based on the relevant guidelines in the general population, lifestyle modifications should probably be applied as the first step of hypertension management in kidney transplant recipients. The optimal pharmacological management of hypertension in kidney transplant recipients is also not clear. Dihydropyridine calcium channel blockers are commonly used as first line agents because of their lack of adverse effects on the kidney, while other antihypertensive drug classes are under-utilised due to fear of the possible haemodynamic consequences on renal function. This review summarizes the existing data on the pathophysiology, diagnosis, prognostic significance and management of hypertension in kidney transplantation.

Allograft dysfunction and parenchymal necrosis associated with renal artery stenosis and perigraft hematoma after kidney transplantation

Transplant renal artery stenosis (TRAS) is one cause of allograft dysfunction. TRAS causes parenchymal necrosis and graft insufficiency. Herein, we report the case of a 40-year-old female with end-stage renal disease due to immunoglobulin A nephropathy, who underwent kidney transplantation with her elder sister. The surgery was successful and the allograft showed primary graft function. At postoperative day (POD) 2, urine output decreased sharply. We checked a non-enhanced abdominal computed tomography scan which showed subcapsular and pelvic cavity hematomas. She underwent hematoma removal surgery with renal upper polar capsulotomy. Bleeding control was successful, but her serum creatinine was 5.4 mg/dL. At POD 25, abdomen magnetic resonance angiography showed significant stenosis at the anastomosis site between the graft renal artery and the recipient’s internal iliac artery. Then, percutaneous transluminal angioplasty was implemented. Significant stenosis (>80%) was detected at the anastomotic site and a 5-mm stent was inserted at stenotic lesion with post-stent balloon angioplasty using a 5-mm balloon catheter. The renal arterial diameter and blood flow were normalized. At postoperative 5 months, a 99mTc dimercaptosuccinic acid scan showed multiple focal radioisotope defects. At 54 months after renal transplantation, her serum creatinine level was 4.0 mg/dL and her glomerular filtration rate was 13 mL/min/1.73 m². Hence, we report that TRAS can cause parenchymal necrosis and allograft dysfunction.

Approach and Management of Hypertension After Kidney Transplantation

Hypertension is one of the most common cardiovascular co-morbidities after successful kidney transplantation. It commonly occurs in patients with other metabolic diseases, such as diabetes mellitus, hyperlipidemia, and obesity. The pathogenesis of post-transplant hypertension is complex and is a result of the interplay between immunological and non-immunological factors. Post-transplant hypertension can be divided into immediate, early, and late post-transplant periods. This classification can help clinicians determine the etiology and provide the appropriate management for these complex patients. Volume overload from intravenous fluid administration is common during the immediate post-transplant period and commonly contributes to hypertension seen early after transplantation. Immunosuppressive medications and donor kidneys are associated with post-transplant hypertension occurring at any time point after transplantation. Transplant renal artery stenosis (TRAS) and obstructive sleep apnea (OSA) are recognized but common and treatable causes of resistant hypertension post-transplantation. During late post-transplant period, chronic renal allograft dysfunction becomes an additional cause of hypertension. As these patients develop more substantial chronic kidney disease affecting their allografts, fibroblast growth factor 23 (FGF23) increases and is associated with increased cardiovascular and all-cause mortality in kidney transplant recipients. The exact relationship between increased FGF23 and post-transplant hypertension remains poorly understood. Blood pressure (BP) targets and management involve both non-pharmacologic and pharmacologic treatment and should be individualized. Until strong evidence in the kidney transplant population exists, a BP of <130/80 mmHg is a reasonable target. Similar to complete renal denervation in non-transplant patients, bilateral native nephrectomy is another treatment option for resistant post-transplant hypertension. Native renal denervation offers promising outcomes for controlling resistant hypertension with no significant procedure-related complications. This review addresses the epidemiology, pathogenesis, and specific etiologies of post-transplant hypertension including TRAS, calcineurin inhibitor effects, OSA, and failed native kidney. The cardiovascular and survival outcomes related to post-transplant hypertension and the utility of 24-h blood pressure monitoring will be briefly discussed. Antihypertensive medications and their mechanism of actions relevant to kidney transplantation will be highlighted. A summary of guidelines from different professional societies for BP targets and antihypertensive medications as well as non-pharmacological interventions, including bilateral native nephrectomy and native renal denervation, will be reviewed.

Aortoiliac Occlusive Disease as a Cause of Allograft Kidney Dysfunction and Refractory Hypertension

Aortoiliac occlusive disease (AIOD), especially proximal to the transplant artery, in kidney transplant patient activates the renin-angiotensin-aldosterone system by limiting graft renal perfusion and causes symptoms that can occur with transplant renal artery stenosis (TRAS) such as refractory hypertension, water retention, and graft renal dysfunction. Immediate clinical suspicion is difficult due to the nature of the progressive disease unlike TRAS. Herein, we present an interesting case of bilateral common iliac artery occlusion (AIOD, TASC II, type C) that manifested as uncontrolled blood pressure and decreased allograft function in a patient who had kidney transplant 17 years ago. The patient was successfully diagnosed with duplex scan, ankle-brachial index (ABI) and computed tomography angiography and treated with percutaneous luminal angioplasty and stent graft insertion.

Risk factors for transplant renal artery stenosis after live donor transplantation

Background

Renal transplant surgeons are making increasing use of live donor kidneys with multiple renal arteries. This study aimed to identify independent risk factors for the development of transplant renal artery stenosis (TRAS) in the modern era of complex arterial reconstruction for multiple vessels.

Methods

Multivariable logistic regression analysis with a stepwise variable deletion model was used to identify risk factors for the development of TRAS in a consecutive series of live donor kidney transplants.

Results

Of 506 kidney transplants, 19 (3·8 per cent) had evidence of significant TRAS on CT angiography. Functional TRAS, defined by improvement in BP control or renal function after correction of a stenosis by angioplasty, occurred in 13 of 506 patients (2·6 per cent). Independent risk factors for TRAS were: use of an explanted internal iliac artery graft from the recipient (odds ratio (OR) 4·95; P = 0·020) and total ischaemia time (OR 1·82; P = 0·010). TRAS was associated with a lower 5-year allograft survival rate (79 versus 88·7 per cent; P = 0·020) but only one graft loss was attributed directly to TRAS. The 5-year allograft survival rate after internal iliac artery grafting was 86 per cent.

Conclusion

Although use of an internal iliac artery graft is an independent risk factor for TRAS after live donor kidney transplantation, this technique is still a useful option for complex arterial reconstruction.

Transplant renal artery stenosis caused by the stretch of an artey branch: a case report and literature review

Background

Renal transplant is the preferred treatment option for these patients with end-stage renal disease. Transplant renal artery stenosis (TRAS) is one of the most common and serious vascular complications after renal transplantation, and most of the TRAS occurred in the anastomosis. The complication must be diagnosed and treated timely, otherwise the function of transplanted kidney may be losed.

Case presentation

A 46-year-old male with end-stage renal disease of unknown cause received a cadaveric renal transplant one year ago. Although three antihypertensive medications were administrated, his blood pressure gradually increased to 190/120 mmHg 3 weeks posttransplantation. Also the level of creatinine increased to 194 μmol/L.Color Doppler ultrasonography indicated a decreased resistance index (RI) in intrarenal arteries and increased blood flow of the transplant renal artery, therefore, a vascular complication of TRAS was suspected. Arteriography was performed and demonstrated TRAS caused by stretch of an artery branch, and the TRAS occurred in the distal site of the anastomosis instead of the anastomosis. Percutaneous transluminal bare stent implantation treatment was successfully performed. Satisfactory clinical efficacy with improvement in transplant renal function and renovascular hypertension was achieved after the interventional treatment.

Conclusion

To our knowledge this is the first reported case of TRAS caused by stretch of an artery branch. When refractory hypertension and allograft dysfunction are presented posttransplantation, TRAS should be suspected. Color Doppler ultrasonography as a non-invasive examination may provide some valuable information, three-dimention CT can be useful for further diagnosis, but is seldom necessary. Arteriography provides the definitive diagnosis of TRAS. Percutaneous transluminal stent implantation treatment of TRAS has high success rate with minimal invasion and complications. When an artery branch situated on the stenosis, a bare stent rather than covered stent is the preferred choice.

[A high level of high-density lipoprotein cholesterol is a protective factor against transplant renal artery stenosis]

OBJECTIVE

To investigate the factors associated with the occurrence of transplant renal artery stenosis (TRAS).

METHODS

A retrospective analysis was conducted in 26 recipients who developed TRAS and 40 concurrent renal recipients without TRAS. We also conducted a nested case-control study in 14 patients with TRAS (TRAS-SD group) and another 14 non-TRAS recipients who received the allograft from the same donor (non-TRAS-SD group).

RESULTS

Compared with those in the concurrent recipients without TRAS, acute rejection (AR) occurred at a significantly higher incidence (P=0.004) and the warm ischemia time (WIT) was significantly longer (P=0.015) and the level of high?density lipoprotein cholesterol (HDL--C) significantly lower (P=0.009) in the recipients with TRAS. Logistic regression analysis suggested that AR (P=0.007) and prolonged WIT (P=0.046) were risk factors of TRAS while HDL-C (P=0.022) was the protective factor against TRAS. In recent years early diagnosis of TRAS had been made in increasing cases, the interval from transplantation to TRAS diagnosis became shortened steadily, and the recipients tended to have higher estimated glomerular filtration rate at the time of TRAS diagnosis.

CONCLUSION

Apart from the surgical technique, AR and prolonged WIT are also risk factors of TRAS while a high HDL-C level is the protective factor against TRAS. The improvement of the diagnostic accuracy by ultrasound is the primary factor contributing to the increased rate of early TRAS diagnosis in recent years.

Evaluation of the efficacy and safety of endovascular management for transplant renal artery stenosis

OBJECTIVES

To evaluate the safety and efficacy of endovascular intervention with angioplasty and stent placement in patients with transplant renal artery stenosis.

METHODS

All patients diagnosed with transplant renal artery stenosis and graft dysfunction or resistant systemic hypertension who underwent endovascular treatment with stenting from February 2011 to April 2016 were included in this study. The primary endpoint was clinical success, and the secondary endpoints were technical success, complication rate and stent patency.

RESULTS

Twenty-four patients with transplant renal artery stenosis underwent endovascular treatment, and three of them required reinterventions, resulting in a total of 27 procedures. The clinical success rate was 100%. All graft dysfunction patients showed decreased serum creatinine levels and improved estimated glomerular filtration rates and creatinine levels. Patients with high blood pressure also showed improved control of systemic blood pressure and decreased use of antihypertensive drugs. The technical success rate of the procedure was 97%. Primary patency and assisted primary patency rates at one year were 90.5% and 100%, respectively. The mean follow-up time of patients was 794.04 days after angioplasty.

CONCLUSION

Angioplasty with stent placement for the treatment of transplant renal artery stenosis is a safe and effective technique with good results in both the short and long term.

Hemodynamics in Transplant Renal Artery Stenosis and its Alteration after Stent Implantation Based on a Patient-specific Computational Fluid Dynamics Model

Background:

Accumulating studies on computational fluid dynamics (CFD) support the involvement of hemodynamic factors in artery stenosis. Based on a patient-specific CFD model, the present study aimed to investigate the hemodynamic characteristics of transplant renal artery stenosis (TRAS) and its alteration after stent treatment.

Methods:

Computed tomography angiography (CTA) data of kidney transplant recipients in a single transplant center from April 2013 to November 2014 were reviewed. The three-dimensional geometry of transplant renal artery (TRA) was reconstructed from the qualified CTA images and categorized into three groups: the normal, stenotic, and stented groups. Hemodynamic parameters including pressure distribution, velocity, wall shear stress (WSS), and mass flow rate (MFR) were extracted. The data of hemodynamic parameters were expressed as median (interquartile range), and Mann–Whitney U-test was used for analysis.

Results:

Totally, 6 normal, 12 stenotic, and 6 stented TRAs were included in the analysis. TRAS presented nonuniform pressure distribution, adverse pressure gradient across stenosis throat, flow vortex, and a separation zone at downstream stenosis. Stenotic arteries had higher maximal velocity and maximal WSS (2.94 [2.14, 3.30] vs. 1.06 [0.89, 1.15] m/s, 256.5 [149.8, 349.4] vs. 41.7 [37.8, 45.3] Pa at end diastole, P = 0.001; 3.25 [2.67, 3.56] vs. 1.65 [1.18, 1.72] m/s, 281.3 [184.3, 364.7] vs. 65.8 [61.2, 71.9] Pa at peak systole, P = 0.001) and lower minimal WSS and MFRs (0.07 [0.03, 0.13] vs. 0.52 [0.45, 0.67] Pa, 1.5 [1.0, 3.0] vs. 11.0 [8.0, 11.3] g/s at end diastole, P = 0.001; 0.08 [0.03, 0.19] vs. 0.70 [0.60, 0.81] Pa, 2.0 [1.3, 3.3] vs. 16.5 [13.0, 20.3] g/s at peak systole, P = 0.001) as compared to normal arteries. Stent implantation ameliorated all the alterations of the above hemodynamic factors except low WSS.

Conclusions:

Hemodynamic factors were significantly changed in severe TRAS. Stent implantation can restore or ameliorate deleterious change of hemodynamic factors except low WSS at stent regions.

Artery Stenosis of the Renal Graft: Experience of a Center of Northeastern Brazil

BACKGROUND

Transplant renal artery stenosis (TRAS), the most common vascular complication after transplant (Tx), leads to resistant hypertension, impaired renal function, and even loss of the graft. The purpose of the study was to investigate the prevalence and factors associated with TRAS in northeastern Brazil.

METHODS

The study was conducted as a retrospective case-control study in a population of Tx recipients in a renal Tx center in northeastern Brazil. Demographic and clinical characteristics of the recipients and donors, data related to the surgery, laboratory data, and number of anti-hypertensive drugs were assessed. Statistical analysis was performed with the use of SPSS 17.0.

RESULTS

A total of 494 of 529 recipients were assessed, of which 24 had TRAS. The prevalence of TRAS was 4.8%. Twelve patients (50%) were men with a mean age of 46.7 ± 13.5 years. The mean time of diagnosis was 89.9 days after Tx. The risk factors associated with TRAS were number of anti-hypertensive drugs ≥2 (odds ratio, 17.0; confidence interval, 4.1 to 70.4; P = .001) and grafting with 2 or more arteries (odds ratio, 8.9; confidence interval, 1.4 to 56.6; P = .021). There was a significant reduction in mean systolic blood pressure (147.1 ± 23.7 to 127.8 ± 15.2 mm Hg, P = .001) and diastolic blood pressure (86.6 ± 13.0 to 77.6 ± 9.4 mm Hg, P = .001) after TRAS repair and in serum creatinine (2.8 ± 2.4 to 1.9 ± 1.8 mg/dL, P = .04).

CONCLUSIONS

Grafts with 2 or more arteries are associated with TRAS, as well as patients who use a higher number of anti-hypertensive drugs. TRAS repair was associated with improved blood pressure control and renal function.

Evaluation of the Vascular Surgical Complications of Renal Transplantation

BACKGROUND

Renal transplantation is the treatment of choice of end-stage renal failure. However, vascular surgical complications can compromise the functional prognosis of the transplant or even be life threatening in the short term. Since few data are available in the literature, the objective of this study was to evaluate the vascular surgical complications of renal transplantation.

METHODS

In a retrospective and monocentric study, the records of all the patients receiving a kidney transplant between January 2008 and December 2014 were reviewed. The demographic data and the follow-up of the patients who presented a vascular surgical complication in relation to their transplant were collected. Minor, intermediate, or major vascular complications were defined according to the need for monitoring, reoperation, or the risk of transplant loss or a life-threatening situation. Predictive factors of vascular complications were also looked for.

RESULTS

Mean age was 50.9 ± 15.0 years, and 312 kidney transplants were carried out (205 men). Fifty vascular surgical complications (16.0%) were found. Among them, 23 vascular complications (7.4%) were major, including 6 (1.9%) which required transplantectomy, after 4 arterial thromboses (1.3%), 1 early venous thrombosis (0.3%), and 1 injury of the inferior vena cava (0.3%). Twelve complications (3.8%) were minor. Surgical revision was necessary in 76% of the vascular complications (n = 38). The average follow-up of the transplanted population was 37.4 ± 24.0 month, 268 kidney transplants (85.8%) were functional and 21 patients (6.7%) returned to dialysis. Surgical complications were more frequent when the recipient had hypertension (P = 0.02, OR = 2.5; 95% CI [1.1-6.1]), in case of right kidney transplant (P = 0.0004, OR = 3.1; 95% CI [1.6-5.8]) and when the kidney hilum consisted of at least arteries (P = 0.02, OR = 10.0; 95% CI [1.3-34]). Male gender (P = 0.03, OR = 0.5; 95% CI [0.3-0.9]) as well as the choice of the common iliac arterial (P = 0.001, OR = 0.4; 95% IC [0.2-0.7]) and venous (P = 0.002, OR = 0.3; 95% IC [0.2-0.8]) axes to carry out the vascular anastomoses appeared as protective factors.

CONCLUSIONS

The vascular surgical complications of kidney transplantation, especially thromboses, can be serious and lead to transplant loss. The expertise of vascular surgeons finds its place here and makes it possible to maintain low rates of vascular complications and loss of transplants.

Femoro-femoral Bypass for Graft Salvage in a Renal Transplant Patient With Aorto-iliac Occlusion: A Case Report

As vascular diseases are becoming more prevalent among renal transplant recipients, complications related to renal artery anastomosis are likely to occur more often. Here we report a renal transplant patient treated with femoro-femoral bypass who had renal allograft dysfunction due to aorto-iliac occlusive disease (AIOD) proximal to renal artery anastomosis. We performed living donor renal transplantation in the left iliac fossa of a 41-year-old male. At post-transplant 30 months, he was admitted with hypertension, increase in serum creatinine, and claudication of his left leg. Doppler ultrasonography showed poor flow characteristics of the renal allograft. Total occlusion of the left common iliac artery was diagnosed on angiography. Since endovascular approach was unsuccessful, we performed right-to-left femoro-femoral bypass to provide retrograde blood flow to the renal allograft. The patient was discharged at postoperative day 3 with decreased serum creatinine, normal blood pressure, no claudication, and normal flow characteristics in Doppler ultrasonography. AIOD should be suspected in renal transplant patients in case of hypertension, allograft dysfunction, and ipsilateral leg ischemia. Femoro-femoral bypass is a safe surgical procedure that may be performed in patients who cannot be treated using an endovascular approach.

Transplant renal artery stenosis: clinical manifestations, diagnosis and therapy

Transplant renal artery stenosis (TRAS) is a well-recognized vascular complication after kidney transplant. It occurs most frequently in the first 6 months after kidney transplant, and is one of the major causes of graft loss and premature death in transplant recipients. Renal hypoperfusion occurring in TRAS results in activation of the renin–angiotensin–aldosterone system; patients usually present with worsening or refractory hypertension, fluid retention and often allograft dysfunction. Flash pulmonary edema can develop in patients with critical bilateral renal artery stenosis or renal artery stenosis in a solitary kidney, and this unique clinical entity has been named Pickering Syndrome. Prompt diagnosis and treatment of TRAS can prevent allograft damage and systemic sequelae. Duplex sonography is the most commonly used screening tool, whereas angiography provides the definitive diagnosis. Percutaneous transluminal angioplasty with stent placement can be performed during angiography if a lesion is identified, and it is generally the first-line therapy for TRAS. However, there is no randomized controlled trial examining the efficacy and safety of percutaneous transluminal angioplasty compared with medical therapy alone or surgical intervention.

Complications of transplantation. Part 1: renal transplants

Vascular complications after solid-organ transplantation are not uncommon and may lead to graft dysfunction and ultimately graft loss. A thorough understanding of the surgical anatomy, etiologies, and types of vascular complications, their presentation, and the options for management are important for managing these complex patients. This article reviews the basic surgical anatomy, vascular complications, and endovascular management options of vascular complications in patients with renal transplants.

Transplant renal artery stenosis secondary to mechanical compression from polycystic kidney disease: A case report

Transplant renal artery stenosis (TRAS) is a potentially treatable cause of allograft dysfunction, hypertension and graft loss. The mainstay of treatment includes angioplasty and endovascular stenting, although observation and surgery are at times indicated. We present an unusual case of TRAS secondary to mechanical compression from a patient's enlarged native polycystic kidneys. This was treated with bilateral native nephrectomy and evidence of TRAS improved both clinically and radiographically. Recognition and treatment are important in preventing irreversible complications of TRAS.

[Exercise-induced renal ischemia after kidney transplantation: report of two cases]

INTRODUCTION

Renal transplant patients are high cardiovascular risk patients. Regular ultrasound surveillance of the renal transplant artery and the iliac artery upstream from the anastomosis is required to detect potential arterial stenosis. The purpose of this article was to illustrate the hemodynamic impact of exercise in such patients and the screening efficiency of Doppler ultrasound stress testing.

METHODS

Two renal transplant patients were hospitalized in our center for impaired renal function, worsening hypertension, and intermittent claudication. This association of peripheral vascular disease and renal dysfunction led us to perform a Doppler ultrasound stress test to search for vascular stenosis upstream from the graft. Hemodynamic fluctuations in the ipsilateral leg were recorded during flexion-extension exercises.

RESULTS

Iliac artery lesions were found in both patients: the Doppler examination showed decreased systolic velocity in the graft artery during exercise, compatible with iliac steal syndrome. Surgical treatment was performed in both patients. After surgery, the control Doppler ultrasound stress test showed that systolic flow did not decline in the graft vessels during exercise. Renal function stabilized in one patient and improved in the other; claudication disappeared after surgery.

CONCLUSION

Doppler ultrasound stress testing can be a valuable tool for detecting exercise-induced renal graft ischemia in transplant patients. Its screening performance should be determined in a larger population before routine use.

[Percutaneous thrombus aspiration in renal artery stenosis after renal transplantation]

We describe the case of a patient with chronic renal failure under hemodialysis for five years who, after renal transplantation, developed acute renal failure and hypertension refractory to medical therapy. Given the clinical and imaging (renal ultrasound and computed tomography) suspicion of renal artery graft thrombosis, invasive angiography was performed, which confirmed the diagnosis. The therapeutic approach consisted of percutaneous thrombus aspiration and subsequent balloon angioplasty of the entire artery, followed by stent implantation in a second procedure. The clinical course was uneventful with improvement of renal function and normalization of blood pressure. The case highlights the importance of percutaneous intervention in the management of patients with vascular complications after transplantation, with successful application of a procedure normally used in the setting of acute myocardial infarction - percutaneous thrombus aspiration and implantation of a drug-eluting vascular stent.

The use of drug-eluting stents in the management of transplant renal artery stenosis

Transplant renal artery stenosis (TRAS) is a common occurrence following kidney transplantation with an incidence rate ranging from 6% to 23%. A single-center retrospective study was conducted to examine the use of drug-eluting stents (DES) in eligible patients with hemodynamically significant TRAS. Between March 2008 and January 2011, 12 patients were diagnosed with TRAS with reference vessel diameter measuring <5 mm and underwent endovascular intervention (EVI) with DES placement. TRAS was detected within the first year posttransplantation in a majority of these patients (83%) and manifested as hypertension (100%), allograft dysfunction (100%) and edema (58%). Procedural success rate was 100%. Patients were followed for a mean period of 16 ± 10 months. Blood pressure improved from a mean of 156/82 to 138/73 mmHg at the end of the follow-up period. In 11/12 patients, serum creatinine improved from 3.1 ± 1.3 mg/dL to 2.3 ± 0.5 mg/dL at the end of the follow-up period. TRAS of early onset is readily amenable to EVI with stent placement resulting in improvement in blood pressure control and allograft function.

Renal artery stenosis in kidney transplants: assessment of the risk factors

BACKGROUND

Transplant renal artery stenosis (TRAS) is an important cause of hypertension and renal allograft dysfunction occurring in kidney transplant recipients. However, conflicting predisposing risk factors for TRAS have been reported in the literature.

OBJECTIVE

The aim of the present study was to assess the potential correlation between possible risk factors and TRAS in a group of living donor renal transplant recipients 1 year after the renal transplantation.

METHODS

We evaluated the presence of renal artery stenosis in 16 recipients who presented with refractory hypertension and/or allograft dysfunction 1 year after renal transplantation. Screening for TRAS was made by magnetic resonance angiography and diagnosis was confirmed by conventional renal angiography. Age, gender, history of acute rejection, plasma lipid profile, serum creatinine, blood urea nitrogen, serum uric acid, calcium phosphate (CaPO₄) product, alkaline phosphatase, fasting blood sugar, hemoglobin, and albumin were compared between the TRAS and non-TRAS groups.

RESULTS

Of 16 kidney transplant recipients, TRAS was diagnosed in three patients (two men and one woman). High levels of calcium, phosphorous, CaPO₄ product, and low-density lipoprotein (LDL) cholesterol were significantly correlated with the risk of TRAS 1 year after renal transplantation (P < 0.05). Serum level of uric acid tended to have a significant correlation (P = 0.051).

CONCLUSION

Correlation between high CaPO₄ product, LDL cholesterol, and perhaps uric acid and TRAS in living donor renal transplant recipients 1 year after renal transplantation might suggest the importance of early detection and tight control of these potential risk factors.

Management of transplant renal artery stenosis

Transplant renal artery stenosis is the most frequent vascular complication of transplantation. Early detection and correction reduce patients' morbidity and allograft dysfunction. Although noninvasive imaging can detect an underlying stenosis, angiography with subsequent angioplasty or stenting, or both, provides definitive diagnosis and treatment. With the introduction of alternative contrast agents and newer catheter and stent technology, these procedures can be performed safely with little risk of contrast-induced nephropathy or allograft loss.

[Vascular complications following renal transplantation: diagnostic evaluation]

Vascular complications after renal transplantation are the most frequent type of complication following urological complications. They may affect the function of the transplant. Early vascular complications include renal artery or vein thrombosis, lesions to the iliac vessels and cortical necrosis. Delayed complications mainly include renal artery stenosis, arteriovenous fistula, and rarely false aneurysm. Doppler sonography, sometimes with the use of intravenous contrast, is the imaging modality of choice in the acute setting or routine follow-up. MRI may be performed for additional morphological and functional evaluation while CT may provide additional evaluation of the arterial supply. Angiography is performed prior to endovascular treatment.

ECG-gated nonenhanced 3D steady-state free precession MR angiography in assessment of transplant renal arteries: comparison with DSA

PURPOSE

To evaluate noncontrast material-enhanced steady-state free precession (SSFP) magnetic resonance (MR) angiography in the assessment of transplant renal arteries (RAs) by using digital subtraction angiography (DSA) as the reference standard.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board; written informed consent was obtained from all participants. In 20 renal allograft recipients scheduled for DSA, the transplant RAs were assessed with electrocardiographically gated nonenhanced SSFP MR angiography performed at 1.5 T; the degree of stenosis was compared with that of DSA. Subjective image quality for SSFP MR angiography was assessed independently by two radiologists on a four-point scale (from 1, nondiagnostic to 4, excellent) in four predefined segments (I, the iliac artery; II, the main transplant artery; III, segmental branches; and IV, parenchymal branches). Sensitivity, specificity, and accuracy of SSFP MR angiography for the detection of relevant (> or =50%) transplant RA stenosis (TRAS) were calculated on a per-artery basis.

RESULTS

One patient was excluded because SSFP MR angiography failed to adequately visualize the allograft vasculature owing to low cardiac output. The mean image quality assessed by both readers was 3.98 +/- 0.16 (standard deviation), 3.5 +/- 0.68, 2.71 +/- 1.12 and 2.03 +/- 1.09 for segments I, II, III, and IV, respectively (kappa = 0.80). DSA helped identify eight relevant (> or =50%) stenoses in six transplant RAs. Kinking of the transplant artery without relevant stenosis was found in seven patients. The degree of stenosis was overestimated in three patients by using SSFP MR angiography. As compared with DSA, the sensitivity, specificity, and accuracy of SSFP MR angiography to help detect relevant TRAS were 100% (six of six), 88% (14 of 16), and 91% (20 of 22), respectively.

CONCLUSION

Nonenhanced SSFP MR angiography is a reliable alternative imaging technique for the assessment of transplant RAs in patients for whom contrast-enhanced MR angiography is contraindicated.

Defining High Risk in Adult Kidney Transplantation

Background

Because identifiable factors contribute to allograft loss, and because no consensus has been reached on the definition of high risk, an interdisciplinary group of nurses, physicians, pharmacists, and social workers was convened in May 2008.

Objective

Participants sought to reach consensus about the current state of science and best practices related to the definition and management of high-risk kidney transplant recipients.

Methods

An expert facilitator with extensive experience in leading consensus teams guided consensus-building activities, which included discussion and small-group work.

Results

This consensus group conceptualized the definition of the “high-risk” kidney transplant recipient and provided information to guide the multidisciplinary team in their assessment of these patients before and after transplant. Three key areas, which were conceptualized as independent scales, had a substantial impact on outcomes: (1) transplant recipient medical factors, (2) donor and recipient immunological factors, and (3) transplant recipient psychosocial factors. Though depicted separately, alteration of a specific risk on one scale could influence some risk factors on another scale. In addition, the kidney allograft itself must be considered in the assessment of high risk.

Conclusions

The continuum of risk described here should be useful to transplant clinicians in their assessment of high-risk adult kidney transplant patients, may aid centers in developing a more complete definition of high risk, and may lead to risk-reduction efforts.

Color duplex sonography in severe transplant renal artery stenosis: a comparison of end-to-end and end-to-side arterial anastomoses

OBJECTIVE

The aim of this study was to investigate differences in Doppler parameters between severe transplant renal artery stenosis (TRAS, arterial lumen reduction >80%) with end-to-end (EE) arterial anastomosis and that with end-to-side (ES) arterial anastomosis.

METHODS

We retrospectively reviewed color duplex sonography (CDUS) and digital subtraction angiography (DSA) images in 38 patients with severe TRAS (19 cases with EE and 19 cases with ES) between January 1, 2000, and December 31, 2006. Doppler parameters were analyzed, including peak systolic velocity (PSV) in the iliac artery, PSV at the arterial anastomosis, PSV in the transplant renal artery, PSV ratio of the stenotic artery/artery proximal to the stenosis, and acceleration time (AT) in the artery distal to the stenosis (in the intrarenal artery). All 38 cases with severe TRAS were initially diagnosed with CDUS and confirmed by DSA.

RESULTS

There were significant differences in PSV in the stenotic artery (P<.01), PSV in the iliac artery (P<.001), and PSV ratios of stenotic artery/artery proximal to the stenosis (P<.001) between arterial anastomosis of EE and that of ES. There was no statistically significant difference in AT in the intrarenal artery between the two types of anastomosis (P>.05).

CONCLUSION

Significantly different PSVs in the stenotic artery, the iliac artery, and the PSV ratio between EE and ES arterial anastomoses should be considered in the interpretation of CDUS when screening for severe TRAS. Different criteria of CDUS need to be established depending on the type of arterial anastomosis in order to improve the accuracy in diagnosing severe TRAS.

Restoration of failed renal graft function after successful angioplasty of pressure-resistant renal artery stenosis using a cutting balloon: a case report

This study is the report of a 37-year-old male with a transplanted kidney from a 3.5-year-old donor: the graft had two arteries transplanted with an aortic patch to an external iliac artery. Four months after transplantation, the graft function deteriorated, together with the development of hypertension. Stenosis of both graft arteries was detected and the patient was referred for angioplasty. The angiographic result was suboptimal, nevertheless, the graft function improved and was more or less stable (serum creatinine, 160-200 micromol/l) for 4 years, along with persistently difficult-to-control hypertension. Five years after transplantation, the graft function deteriorated again and severe graft artery restenosis was detected. The restenosis did not respond to dilatation, graft function failed, hypertension decompensated, and left ventricular failure developed. The patient required dialysis. A cutting balloon angioplasty opened the artery, and kidney function was restored after a few days: the serum creatinine level dropped to 140-160 micromol/l, and the glomerular filtration rate (creatinine clearance) to 0.65 ml/min/1.73 m(2). The graft function has now been stable for more than 2 years, however, the hypertension is still difficult to control.

Long-term follow-up of renal transplant patients with renal artery stenosis treated by percutaneous angioplasty

PURPOSE OF THE STUDY

To evaluate if renal angioplasty (PTRA) in patients with transplanted kidney and renal artery stenosis (TRAS) can have long-term effect on hypertension and renal function.

MATERIALS AND METHODS

Within a 24-year time period, 58 PTRAs in 55 adults (three times Re-PTRA) with transplanted kidney were performed. The group included 34 males and 21 females, average age 41+/-10.6 (18-72) years. After exclusion of 7 technical failures, 51 PTRAs were followed at 1 week, 6 months and 1-3 years after PTRA. Hypertension improvement was defined as mean arterial pressure (MAP) decrease of at least 15% from the pre-PTRA value. Graft function was evaluated by serum creatinine (Scr) and creatinine clearance (Ccr) levels, and the improvement was defined as a 20% change. Clinical FU was 3 years.

RESULTS

PTRA technical success was 88.4%. In 51 kidney recipients at the end of FU, blood pressure improved in 65.2% of patients (MAP decreased from 123+/-13.1 to 107+/-12.1 mmHg), but no patient remained normotensive medication free. Graft function improved in 44.8% of patients and was stabilized in 20.7% of them (average Ccr before PTRA: 0.48+/-0.29, after PTRA: 0.78+/-47 ml/s). PTRA complications were observed in 25.5% of procedures, most often with no clinical sequel. Thirty days mortality was 1.8% (one patient).

CONCLUSIONS

PTRA results in kidney recipients are valuable mainly in preserving graft function.

Iliac artery stenosis as a cause of posttransplant renal failure and claudication

Iliac artery stenosis (IAS) is a rare complication after renal transplantation. We demonstrate a case of ipsilateral external IAS proximally to anastomosis in a kidney recipient, which manifested with renal failure and claudication, and was successfully treated with endovascular stent placement.

The Impact of Recipient History of Cardiovascular Disease on Kidney Transplant Outcome

Cardiovascular disease (CVD) leads to increased mortality rates among renal transplant recipients; however, its effect on allograft survival has not been well studied. The records from the United States Renal Data System and the United Network for Organ Sharing from January 1, 1995, through December 31, 2002, were examined in this retrospective study. The outcome variables were allograft survival time and recipient survival time. The primary variable of interest was CVD, defined as the presence of at least one of the following: cardiac arrest, myocardial infarction, dysrhythmia, congestive heart failure, ischemic heart disease, peripheral vascular disease, and unstable angina. The Cox models were adjusted for potential confounding factors. Of the 105,181 patients in the data set, 20,371 had a diagnosis of CVD. The presence of CVD had an adverse effect on allograft survival time (HR 1.12, p < 0.001) and recipient survival time (HR 1.41, p < 0.001). Among the subcategories, congestive heart failure (HR 1.14, p < 0.005) and dysrhythmia (HR 1.26, p < 0.05) had adverse effects on allograft survival time. In addition to increasing mortality rates, CVD at the time of end-stage renal disease onset is also a significant risk factor for renal allograft failure. Further research is needed to evaluate the role of specific forms of CVD in allograft and recipient outcome.

Contrast-enhanced MR angiography (CE-MRA) in the evaluation of vascular complications of renal transplantation

Vascular complications associated with renal transplantation merit urgent investigation since they are often correctable, and timely intervention can help salvage the graft kidney. Contrast-enhanced MR angiography (CE-MRA) is a promising non-invasive technique, uses relatively non-nephrotoxic contrast agents and can rapidly demonstrate the underlying lesion in most instances. In this pictorial review we present the spectrum of abnormalities, as well as the pitfalls of interpretation of CE-MRA, that we encountered in 41 cases where there was clinical suspicion of vascular complications of renal transplantation. We believe that CE-MRA is a valuable, non-invasive screening technique in these cases, and further investigation and management of these patients can be confidently tailored to the results of the CE-MRA study.

Renal artery stenosis in patients with peripheral vascular disease in Kuwait

OBJECTIVE

The aim of this study was to identify the incidence of atherosclerotic renal artery stenosis (RAS) in patients with peripheral vascular disease (PVD) and its relation to any known risk factors.

SUBJECTS AND METHODS

This prospective study was conducted on 212 patients who were subjected to peripheral angiography for symptoms of PVD over a 3-year period from 1995 to 1998 at the Mubarak Al-Kabeer Hospital, Kuwait. Angiographic evidence of atherosclerotic disease and its severity was recorded in renal, abdominal aorta, iliac, femoral, popliteal and below-knee arteries. In addition, a detailed search of identifiable risk factors was done using history, clinical examination and laboratory studies.

RESULTS

The incidence of significant atherosclerotic RAS (more than 50% diameter stenosis) in patients with PVD was 15/212 (7.07%) with no significant difference in ratio between males and females (p = 0.3) compared to that of PVD alone. Patients with common iliac and femoral artery lesions had a high incidence of RAS (93.3 and 86.7%, respectively) with more than 80% probability in RAS patients with involvement of these vessels. There was significant renal impairment (p < 0.005), as assessed by serum creatinine levels, in patients with RAS compared to those who did not have it. There was a high incidence of smoking in patients with RAS (p = 0.02), and smoking was the only risk factor identified in these subjects.

CONCLUSIONS

Patients with iliac or femoral atherosclerotic disease have a high probability of associated RAS. Presence of renal impairment in patients with PVD is highly indicative of RAS. Smoking is the only identified risk factor for RAS in association with PVD in our population.

Management of arterial stenosis affecting kidney graft perfusion: a single-centre study in 53 patients

We assessed clinical and duplex sonographic (CDS) findings, and outcome in patients with stenosis of the transplant renal artery (TRAS) or the aorto-iliac segment proximal to the graft (Prox-TRAS) treated with dilatation (PTA), stenting (PTAS) and surgery. From 1988 to 2002, of 1189 patients with renal transplantations, 117 underwent angiography. Fifty-three patients with TRAS (n = 37)/Prox-TRAS (n = 16) were found (4.4%). Clinical presentation included deterioration of hypertension (144 +/- 15/84 +/- 9, 157 +/- 22/90 +/- 10 mmHg; p < 0.001), increase of creatinine (1.7 +/- 0.9, 2.5 +/- 1.3 mg/dL; p = 0.01) and renal failure (n = 12). CDS indicated insufficient perfusion and differentiated between TRAS and Prox-TRAS. From renal transplantation (RTX) until the detection of stenosis pulsatility indices (PI) decreased from 1.2 +/- 0.46 to 0.98 +/- 0.29; (p = 0.001). Fifty-two patients underwent invasive treatment (21 PTA, 10 PTAS and 21 surgery) after which hypertension and creatinine significantly improved. PI increased. Restenosis occurred in 16 (52%) cases of the interventional (PTA 62% and PTAS 30%) and in 3 (14%) of the surgical group (p = 0.011). Hypertension and graft dysfunction due to perfusion problems are rare. Clinical findings are nonspecific but CDS findings are helpful to select patients for angiography. Invasive treatment leads to clinical improvement. Surgery yields better results than PTA, but additional stenting will probably improve the outcome of angioplasty.

Transplant renal artery stenosis: outcome after percutaneous intervention

PURPOSE

To assess the outcome of percutaneous transluminal angioplasty (PTA) and stent placement as the primary treatment for transplant renal artery stenosis (TRAS).

MATERIALS AND METHODS

A retrospective review of PTA and stent placement procedures performed for TRAS from April 1997 to July 2003 was conducted. Reviewed parameters included technical success, date of transplantation, dates of percutaneous intervention, mean arterial blood pressure, number of blood pressure medications, and serum creatinine level before and after intervention. Twenty-one interventions were performed in 18 allografts. The primary clinical indication for imaging and treatment was increased creatinine level in 12 allografts and hypertension in six allografts. Patency rates were estimated with use of the Kaplan-Meier method.

RESULTS

The technical success rate of PTA/stent placement was 100% and the clinical success rate was 94% (17 of 18 allografts). Thirteen interventions involved PTA alone, with eight combined PTA and stent insertions. The mean preintervention serum creatinine level among 12 allografts presenting with elevated creatinine levels was 2.8 mg/dL +/- 1.4 (SD), compared with a 1-month postintervention mean of 2.2 mg/dL +/- 0.7 (P = .03). Of six allografts that presented with hypertension, significant improvement was seen between the preintervention and 1-month postintervention mean systolic (174 mm Hg vs 135 mm Hg, P = .003) and diastolic (99 mm Hg vs 82 mm Hg, P = .02) pressures. These patients required a mean of 2.3 medications for blood pressure control before intervention, compared with a mean of 1.0 medications at 1 month after intervention (P = .002). Primary patency rates at 3, 6, and 12 months (+/-95% CI) were 94% +/- 6%, 72% +/- 12%, and 72% +/- 12%, respectively. Secondary patency rates at 3, 6, and 12 months (+/-95 CI) were 100%, 85% +/- 10%, and 85% +/- 10%, respectively. Mean follow-up time was 27 months. Of the eight allografts that underwent stent placement, all eight remained patent at last follow-up (mean, 18.3 months +/- 9.2). One major complication of a puncture site pseudoaneurysm occurred (5%).

CONCLUSION

Primary treatment of TRAS with PTA with or without stent placement has good intermediate-term patency and is associated with significant early improvement in blood pressure and creatinine level.