Assessment and Management of Transplant Renal Artery Stenosis. A Literature Review.

BACKGROUND: Transplant renal artery stenosis (TRAS) following kidney transplantation is a possible cause of graft failure. This review aimed to summarize the evidence about physiopathology, diagnosis and early and late effectiveness of the endovascular treatment (EVT), including angioplasty and stenting procedures. METHODS: A literature research was performed using Pubmed, Scopus and the Cochrane Library databases (January 2000-September 2020) according to PRISMA guidelines. Studies were included if they describe EVT, percutaneous transluminal angioplasty or stent placement of TRAS, published in English and with a minimum of ten patients. RESULTS: Fifty-six studies were included. TRAS incidence ranges from 1% up to 12% in transplanted kidneys. The TRAS risk factors were: elderly donor and recipient, cytomegalovirus match status, Class II Donor Specific Antibodies (DSA), expanded donor criteria, delayed graft functioning and other anatomical and technical factors. The highest frequency of TRAS presentation is after 3-6 months after kidney transplantation. The most frequent localization of stenosis was para-anastomotic (ranging from 25% to 78%). In 9 studies, all patients were treated by percutaneous transluminal angioplasty (PTA), in 16 studies all patients received percutaneous transluminal stenting (PTS) and in 21 series patients received either PTA or PTS. The twelve months patency rates after EVT ranged from 72% to 94%. The overall complication rate was 9%, with pseudoaneurysms and hematomas as most frequent complications. CONCLUSIONS: TRAS can be successfully and safely treated through an endovascular approach. Stent delivery seems to guarantee a higher patency rate compared to simple angioplasty, however further studies are needed to confirm these results.

Endovascular treatment of transplant renal artery stenosis based on hemodynamic assessment using a pressure wire: a case report.

BACKGROUND: Transplant renal artery stenosis (TRAS) is a serious complication after renal transplantation, leading to hypertension, deterioration in renal function, and/or graft loss. The incidence of TRAS reportedly varies from 1 to 23%, depending on its definition or diagnostic tools. The hemodynamic definition or therapeutic indication of TRAS is unclear. CASE PRESENTATION: A 66-year-old man with a history of diabetes, chronic kidney disease, and angina presented with a 2-week history of dyspnea and leg edema. He had undergone living-donor kidney transplantation for end-stage renal disease secondary to diabetic nephropathy 7 years earlier. He developed acute deterioration in renal function after the administration of an angiotensin II receptor blocker and required emergency hospitalization owing to acute congestive heart failure with pulmonary edema. A vasodilator and loop diuretics were administered following his admission, and the patient's symptoms resolved quickly. Further investigation, including magnetic resonance angiography and ultrasonography, revealed severe stenosis of the transplant renal artery. Renal arteriography and pressure gradient measurement using a 0.014-inch pressure wire were performed. The systolic pressure gradient was 40 mmHg, and the resting Pd/Pa ratio (ratio of mean distal to lesion and mean proximal pressures) was 0.90 without hyperemia. Hemodynamically significant stenosis was suspected. Intravascular ultrasonography revealed vessel shrinkage in the stenotic area, suggestive of the end-to-end anastomosis site. Pre-dilation using a 4-mm balloon, implantation of a 6-mm self-expandable stent, and post-dilatation using a 5-mm balloon were performed. Although the moderate stenosis persisted angiographically, the systolic pressure gradient dropped to 20 mmHg with the mean systolic pressure ratio increased to 0.95, which was considered an acceptable result. One month after the procedure, the patient's renal function and blood pressure control had significantly improved. CONCLUSIONS: Hemodynamic assessment using a pressure wire is useful in determining the appropriate therapeutic indication and endpoint of endovascular treatment of TRAS.

Comparison of ferumoxytol-enhanced MRA with conventional angiography for assessment of severity of transplant renal artery stenosis.

PURPOSE: To determine the accuracy of ferumoxytol-enhanced magnetic resonance angiography (MRA) in assessing the severity of transplant renal artery stenosis (TRAS), using digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: Our Institutional Review Board approved this retrospective, Health Insurance Portability and Accountability Act-compliant study. Thirty-three patients with documented clinical suspicion for TRAS (elevated serum creatinine, refractory hypertension, edema, and/or audible bruit) and/or concerning sonographic findings (elevated renal artery velocity and/or intraparenchymal parvus tardus waveforms) underwent a 1.5T MRA with ferumoxytol prior to DSA. All DSAs were independently reviewed by an interventional radiologist and served as the reference standard. The MRAs were reviewed by three readers who were blinded to the ultrasound and DSA findings for the presence and severity of TRAS. Sensitivity, specificity, and accuracy for identifying substantial stenoses (>50%) were determined. Intraclass correlation coefficients (ICCs) were calculated among readers. Mean differences between the percent stenosis from each MRA reader and DSA were calculated. RESULTS: On DSA, a total of 42 stenoses were identified in the 33 patients. The sensitivity, specificity, and accuracy of MRA in detecting substantial stenoses were 100%, 75-87.5%, and 95.2-97.6%, respectively, among the readers. There was excellent agreement among readers as to the percent stenosis (ICC = 0.82). MRA overestimated the degree of stenosis by 3.9-9.6% compared to DSA. CONCLUSION: Ferumoxytol-enhanced MRA provides high sensitivity, specificity, and accuracy for determining the severity of TRAS. Our results suggest that it can potentially be used as a noninvasive examination following ultrasound to reduce the number of unnecessary conventional angiograms. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:779-785.

Comparing the diagnostic accuracy of contrast-enhanced computed tomographic angiography and gadolinium-enhanced magnetic resonance angiography for the assessment of hemodynamically significant transplant renal artery stenosis.

To compare diagnostic accuracy of contrast-enhanced computed tomographic angiography (CTA) and gadolinium-enhanced magnetic resonance angiography (MRA) for the assessment of hemodynamically significant transplant renal artery stenosis (TRAS). After institutional review board approval, records of 27 patients with TRAS confirmed on digital subtraction angiography (DSA) were retrospectively reviewed. A total of 13 patients had MRA and 14 had CTA before DSA. Two board-certified fellowship-trained radiologists, one each from interventional radiology and body imaging blindly reviewed the DSA and CTA or MRA data, respectively. Sensitivity (SN), specificity (SP), positive predictive value, and negative predictive value of MRA and CTA were estimated using 50% stenosis as the detection threshold for significant TRAS. These parameters were compared between modalities using the Fisher exact test. Bias between MRA or CTA imaging and DSA was tested using the Wilcoxon signed-rank test. Two patients were excluded from the MRA group owing to susceptibility artifacts obscuring the TRAS. The correlation between MRA and DSA measurements of stenosis was r = 0.57 (95% CI:-0.02, 0.87; P = 0.052) and between CTA and DSA measurements was r = 0.63 (95% CI: 0.14, 0.87; P = 0.015); the difference between the 2 techniques was not significant (P = 0.7). Both imaging modalities tended to underestimate the degree of stenosis when compared with DSA. MRA group (SN and SP: 56% and 100%, respectively) and CTA group (SN and SP: 81% and 67%, respectively). There were no significant differences in detection performance between modalities (P>0.3 for all measures). We did not find that either modality had any advantage over the other in terms of measuring or detecting significant stenosis. Accordingly, MRA may be preferred over CTA after positive color Doppler ultrasound screening when not contraindicated owing to lack of ionizing radiation or nephrotoxic iodinated contrast. However, susceptibility of artifacts owing to surgical clips at the anastomosis may limit diagnostic utility of MRA as found in 2 of 13 patients. Trend towards no significant difference between the CTA and enhanced MRA in the detection of hemodynamically significant TRAS.

Renal artery stenosis: prevalence of, risk factors for, and management of in-stent stenosis.

Atherosclerotic renal artery stenosis is common and is associated with hypertension and chronic kidney disease. More frequent use of percutaneous renal artery stent placement for the treatment of renal artery stenosis during the past 2 decades has increased the number of patients with implanted stents. In-stent stenosis is a serious problem, occurring more frequently than earlier reports suggest and potentially resulting in late complications. Currently, there are no guidelines covering the approach to restenosis after renal artery stent placement. This article reviews data on the prevalence of and risk factors for the development of in-stent stenosis and the clinical manifestations, evaluation, and treatment of in-stent stenosis and suggests a strategy for the management of patients after percutaneous renal artery stent placement.

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.

[Comparison of quantitative computerized angiography and intravascular ultrasound in assessment of renal artery stenosis in patients with renovascular hypertension treated with percutaneous transluminal angioplasty with concomitant intravascular brachytherapy]. / Porównanie ilosciowej angiografii i ultrasonografii wewnatrznaczyniowej w ocenie zwezenia resztkowego i restenozy u chorych z nadcisnieniem naczyniowo- nerkowym leczonych metoda przezskórnej angioplastyki tetnicy nerkowej i brachyterapii sródnaczyniowej.

UNLABELLED: Renal Angiography and IntraVascular UltraSonography (IVUS), are valuable diagnosis methods for assessment of renovascular hypertension (RVH). Endovascular techniques employing percutaneous transluminal renal angioplasty (PTRA) are effective for therapy of ischaemic nephropathy in patients with RVH. Success of PTRA is limited by a significant rate of restenosis. THE AIM OF STUDY was to compare the assessment of residual stenosis and restenosis with angiography and IVUS. MATERIAL AND METHODS: Residual stenosis after PTRA (combine with intravascular brachyterapy in 33 patients--group I) were assessed in 62 RVH patients with angiography and IVUS techniques. Both baseline and 9-month follow-up quantitative computerized angiography (QCA) and intravascular ultrasound (IVUS) analysis were performed to assess restenosis. RESULTS: Residual stenosis after PTRA of atherosclerotic lesions was slightly lower with QCA than IVUS (in group I 15.49 +/- 4.69% and 18.81 +/- 4.81% and in group II 15.36 +/- 4.68% and 18.43 +/- 4.69%, respectively). The loss of lumen area in QCA assessment was slightly greater than in IVUS measurement (1.2 +/- 0.7 mm vs. 0.9 +/- 0.8 mm in group I i 1.7 +/- 0.7 mm vs. 1.5 +/- 0.8 mm in group II). The angiographic measurements of late lumen loss, diameter stenosis, and minimal lumen diameter correlated well with IVUS measurements (r = 0.81, r = 0.89 and r = 0.89 respectively). CONCLUSIONS: Angiography and IVUS are equally effective methods for diagnosis and assessment of residual stenosis and restenosis after endovascular renal artery revascularisation.

Assessment of renal artery fibromuscular dysplasia: angiography, intravascular ultrasound (with virtual histology), and pressure wire measurements.

Fibromuscular dysplasia (FMD) of the renal arteries is classically associated with secondary hypertension in younger individuals, which may be treatable and even curable by percutaneous transluminal renal angioplasty. Angiography of these renal arteries often displays "beaded" luminal abnormalities. The angiographic findings, however, may not accurately reflect the severity or precise location of the intraluminal obstruction. We present a case of an older individual with longstanding hypertension and FMD, in whom the use of a coronary pressure wire and intravascular ultrasound enabled precise localization and treatment of the hemodynamically significant stenosis. Virtual histology of FMD in the renal vasculature is also reported.

Suprarenal fixation of endovascular aortic stent grafts: assessment of medium-term to long-term renal function by analysis of juxtarenal stent morphology.

OBJECTIVE: The effect of suprarenal stent fixation during endovascular aortic aneurysm repair (EVAR) on renal function remains unclear. A unique validated three-dimensional intraluminal imaging technique was used to analyze the effect of suprarenal stent position relative to renal artery orifices. Also analyzed was its medium-term to long-term effects on renal function. METHODS: The study cohort comprised 29 of 34 consecutive patients who underwent EVAR with the Zenith endograft system from September 1999 to March 2002 at a single institution. The precise locations of the uncovered suprarenal stent struts were assessed by a virtual endoscopic imaging technique. Anatomic and quantitative categorization of patients was made according to the configuration of uncovered stent struts across the renal artery ostia (RAO). The anatomic subgroups were defined as struts located centrally or peripherally across both RAO. The quantitative subgroups were defined as RAO crossed by multiple struts, a solitary strut, or no struts. The subgroups were compared for their renal function, as assessed by temporal measurements of serum creatinine concentration and creatinine clearance, and renal parenchymal perfusion defects, as assessed using contrast-enhanced computed tomography (CT). RESULTS: Mean follow-up was 52.7 months. Separate subgroup analysis for both anatomic and quantitative configurations did not demonstrate any significant difference in renal function between the different strut permutations (P > .05). Follow-up imaging confirmed one case of renal infarction secondary to an occluded accessory renal artery, although this patient had normal serum creatinine levels. CONCLUSION: RAO coverage by suprarenal uncovered stents does not appear to have a significant effect on renal function as evaluated by creatinine measurements in patients with normal preoperative renal function.

Fibromuscular dysplasia of renal arteries: percutaneous revascularization based on hemodynamic assessment with a pressure measurement guidewire.

Fibromuscular dysplasia (FMD) leading to renal artery stenosis and hypertension is one of the most common treatable causes of secondary hypertension. However, frequently it can be difficult to judge the anatomical severity of a stenotic lesion with various noninvasive and invasive imaging modalities. We present two patients with poorly controlled hypertension and FMD affecting the renal arteries, in whom there were no anatomically significant stenoses by renal magnetic resonance angiography or selective renal artery angiography. Utilizing a 0.014'' high fidelity micromanometer tipped PressureWire XT (Radi, Reading, MA), to measure intravascular pressure gradients throughout the diseased renal arteries, we identified physiologically significant stenoses, and successfully treated both patients with percutaneous transluminal angioplasty.

Colour-coded duplex sonography in the diagnostic assessment of vascular complications after kidney transplantation in children.

BACKGROUND: Vascular complications are a major cause of dysfunction or transplant loss in children. Arterial or venous occlusion, transplant renal artery stenosis (TRAS) and some arteriovenous (AV) fistula require rapid detection and prompt intervention. The present study was performed to determine the accuracy of colour Doppler sonography (CDS) in the early and late phase after renal transplantation and to correlate the results with angiographic and intraoperative findings. OBJECTIVE: CDS is the preferred imaging modality with a high diagnostic accuracy for follow-up of renal transplantation in children. The indication for angiography should be established on the basis of the CDS diagnosis. MATERIALS AND METHODS: In 87 children (mean age 10.9 years, range 2-17), 423 CDS examinations were performed after renal transplantation. Angiography was performed in 17 cases; surgery was necessary in 16 patients. RESULTS: CDS correctly identified 8/8 arterial or venous occlusions and 7/7 TRAS. The only false positive diagnosis of TRAS was due to misinterpretation of an iliac artery stenosis. Six AV fistulae were diagnosed by CDS. The overall positive predictive value of CDS was 94 % in this study. CONCLUSION: CDS is a noninvasive, non-radiation producing imaging modality with a high diagnostic accuracy. It is the method of choice in the assessment of vascular complications after renal transplantation in children.

Supra- and juxtarenal aneurysms of the abdominal aorta: preoperative assessment with thin-section spiral CT.

PURPOSE: To assess the contribution of thin-section spiral computed tomography (CT) to the preoperative radiologic evaluation of juxta- and suprarenal abdominal aortic aneurysms. MATERIALS AND METHODS: Thirty-eight patients (26 men, 12 women; age range, 60-81 years) with infrarenal (n = 23), juxtarenal (n = 8), and suprarenal (n = 7) aneurysms underwent digital subtraction angiography (DSA) and 2-mm-collimation spiral CT. Cine-interactive display of overlapping axial, reformatted, and maximum intensity projection images were used for CT image analysis. CT findings were compared with angiographic and surgical findings. RESULTS: The proximal extent of the juxta- and suprarenal aneurysms (n = 15) could be correctly predicted in 12 cases (80%) with DSA and was exactly determined in 14 (93%) with CT. All renal arteries except three accessory renal arteries were correctly depicted with spiral CT (83 of 86 [96%]). With DSA as the standard of reference, renal artery stenoses of at least 70% were accurately assessed in 95% of cases. CONCLUSION: Thin-section spiral CT can provide additional information in the preoperative diagnosis of juxta- and suprarenal aneurysms.

[Assessment of arterial hypertension associated with renal transplantation using Doppler ultrasonography]. / Evaluación mediante eco-Doppler de la hipertensión arterial asociada al trasplante renal.

OBJECTIVES: The incidence of arterial hypertension post-renal transplantation has been reported to be 48.6%. The present study investigated the usefulness of echo Doppler in detecting renal artery stenosis and the effects of arterial pressure control and hypotensive agents on the vascular resistance of the renal graft. METHODS: A total of 234 echo Doppler studies were done in 110 patients. The pulsatility index (PI), resistance index (RI), acceleration and mean velocity (MV), maximum systolic (SVMX) and minimum diastolic (DVMN) velocities of the external iliac, renal, segmental, interlobar and arcuate arteries were determined. RESULTS: In the stenotic segment, an elevation of SVMX was observed, followed by turbulent flow in the post-stenotic segment in 73% of the cases with arterial stenosis. The hypertensive patients had a higher external iliac artery RI than the normotensives. The beta-blockers reduced the RI in large vessels (external iliac), the vasodilators in medium-sized extraparenchymal vessels (segmental) and the calcium antagonists changed the PI in the smaller caliber intraparenchymal vessels (interlobar and arcuate). CONCLUSIONS: Evaluation by echo Doppler is the first diagnostic approach in patients suspected as having arterial stenosis of the renal graft. It permits evaluating blood flow changes from hypertension and hypotensive agents.

Estenosis de arteria renal: características angiográficas en 210 casos / Stenosis or the renal artery: angiographic characteristics in 210 cases

Se presentan 210 casos de enfermos portadores de lesiones estenosantes de arteria renal, estudiados en el Departamento de Angiología del Hospital de Especialidades del Centro Médico Nacional, durante un periodo de 29 años (1963-1992), documentados angiográficamente. La indicación del estudio fue la hipertensión arterial severa y las manifestaciones de insuficiencia arterial crónica de miembros inferiores, así como enfermedad aortoiliaca. De estos casos, 92 correspondieron al sexo femenino y 118 al masculino. La edad varió de 9 a 76 años. En cuanto a la localización de la lesión de la arteria renal, en 58 casos, fue en el ostium y/o en el tercio proximal y, en 50 de ellos, la lesión fue bilateral y estaba asociada a otras lesiones del territorio aórtico y correspondieron a mujeres jóvenes los cuales se consideraron de etiología inflamatoria (artritis). En otros 75 casos, la lesión se localizó en el tercio medio con estenosis única o múltiple, y extensión al tercio distal, en la mayoría fue unilateral y solamente en 15 casos, la lesión estaba presente en forma bilateral. Estos casos predominaron en el sexo masculino, entre la tercera y cuarta década de la vida y correspondieron a discplasia fibromuscular. En cambio en los 65 casos restantes, la lesión estenosante se presentó en personas de la sexta década de la vida predominando también en el sexo masculino, donde la angiografía mostró lesiones muy importantes del eje aortoiliaco y se consideraron de origen ateroscleroso. En 12 casos, la estenosis estuvo en relación a otras patologías. Algunos de estos casos fueron sometidos a procedimientos quirúrgicos, del tipo de las derivaciones arteriales, angioplastia transluminal y en los últimos años al autotrasplante renal (descenso renal), con excelentes resultados

Preoperative assessment of abdominal aortic aneurysm: the value of helical and three-dimensional computed tomography.

PURPOSE: The purpose of this study was to evaluate the utility of helical computed tomography (CT) in the preoperative assessment of abdominal aortic aneurysms (AAA) and to compare its accuracy with aortography and operative findings. METHODS: Thirty-two patients with suspected AAA were evaluated by helical CT with either 5 mm collimation (slice thickness) or a combination of 3 mm collimation through the renal and mesenteric arteries and 7 mm collimation through the remainder of the AAA. Three-dimensional reconstructions were performed with use of three different techniques, and results were compared with aortography and surgery. RESULTS: Twenty-five patients were found to have an aneurysm, and 19 subsequently underwent surgery. Standard angiography was also performed in 13. The location, size, and extent of the aneurysm, as well as the wall calcification and intraaneurysmal thrombus, were well depicted with helical CT. The visceral aortic branches, including the detection of renal artery stenosis and accessory renal arteries, were consistently seen with the 3 mm/7 mm collimation protocol and three-dimensional reconstruction. CONCLUSION: Helical CT with three-dimensional display of the aorta and its branches combines the advantages of conventional CT imaging and aortography. This technique appears to provide comprehensive preoperative evaluation of AAA.

Angiographic assessment of renal artery pathology: how reliable?

The accuracy of the angiographic interpretation of the histologic type of renal artery stenosis was assessed using a renal pathologist's diagnosis as the "gold standard." The angiograms of 42 renal artery stenoses were interpreted without other information, except age and gender, independently by six angiographers. This assessment indicated that angiography is not an accurate means by which to distinguish between the individual types of fibromuscular disease of the renal artery. However, it is a fairly accurate means by which to distinguish fibromuscular disease in general from atherosclerosis of the renal artery, 207 (82%) correct interpretations of 252. In addition, in the presence of renal artery stenosis, the absence of abdominal aortic atherosclerosis on angiography is an excellent predictor of fibromuscular renal artery disease, 17 (94%) of 18 specimens. Likewise, in the presence of a renal artery stenosis, angiographically demonstrable abdominal aortic atherosclerosis is a fair predictor of atherosclerotic renal artery disease, 16 (76%) of 21 specimens.