Transluminal angioplasty of transplanted renal artery stenosis: a review of the literature for its safety and efficacy

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.

The role of MR imaging in the assessment of renal allograft vasculature

Renal allograft dysfunction after transplantation is a relatively common occurrence with various potential etiologies. Vascular etiologies are of particular importance as early surgical or minimally invasive intervention can, in some cases, salvage the graft. Diagnosis of vascular pathology resulting in allograft dysfunction requires a thorough workup, of which imaging is a key component. Generally, ultrasound is the first-line imaging modality. More recently, MRI has been shown to be an effective and safe modality for diagnosis of vascular pathology after renal transplantation, particularly for diagnosis of transplant renal artery stenosis. This review will summarize imaging modalities that are most commonly used in evaluating vascular pathology after renal transplantation, with a focus on the various contrast- and non-contrast-enhanced MR techniques described in the literature and used at our institution. Of particular interest is the relatively recent utilization of the non-gadolinium containing iron-based contrast agent, ferumoxytol, in time-resolved contrast-enhanced MR angiography.

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.

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.

Restoration of renal allograft function via reduced-contrast percutaneous revascularization of transplant renal artery stenosis

Transplant renal artery stenosis (TRAS), the most common vascular complication of kidney transplantation, can lead to heart failure, uncontrolled hypertension, and irreversible dysfunction of the transplanted kidney. Percutaneous revascularization can improve outcomes in well-selected patients with symptomatic TRAS, but the intervention itself poses risk to the transplanted kidney because of the quantities of nephrotoxic contrast solution that often are used. We report the case of a patient with TRAS who, 5 months after undergoing a kidney transplant, developed allograft dysfunction and heart failure that required hemodialysis. We performed angioplasty and stenting of the TRAS, using intravascular ultrasonography and fluoroscopy as our primary imaging methods. To minimize further damage to a potentially viable kidney, the volume of intravascular contrast medium used was trivial (a total of 9 cc). Revascularization of the patient's TRAS restored his renal function: within 4 weeks of the procedure, he no longer needed hemodialysis, and his heart failure symptoms had resolved. This case emphasizes the value of early definitive treatment of TRAS and the usefulness of intravascular ultrasonography to minimize the amount of contrast medium used in endovascular procedures.

Renal Transplant Complications: Diagnostic and Therapeutic Role of Radiology

Kidney was the first and is the most frequently transplanted organ. Despite improved surgical techniques and transplantation technology, complications do occur and, if left untreated, may lead to catastrophic consequences. Renal transplantation complications may be vascular (eg, renal artery and vein stenosis and thrombosis, arteriovenous fistula, and pseudoaneurysms); urologic (eg, urinary obstruction and leak, and peritransplantation fluid collections, including hematoma, seroma, lymphocele, and abscess formation); and nephrogenic, including acute tubular necrosis, graft rejection, chronic allograft nephropathy, and neoplasm. Early diagnosis and treatment of these complications are paramount to prevent graft failure and other significant morbidities to the patients. Radiology plays a pivotal role in the diagnosis and treatment of these complications, with minimally invasive percutaneous techniques. In this article, we reviewed renal transplantation anatomy, a wide range of complications that may occur after renal transplantation surgery, typical imaging appearances of the complications on varies imaging modalities, and percutaneous interventional techniques that are used in their treatment.

Transplant renal artery stenosis in children: risk factors and outcome after endovascular treatment

BACKGROUND

Transplant renal artery stenosis (TRAS) is an increasingly recognised cause of post-transplant hypertension.

METHODS

We retrospectively analysed 216 paediatric renal recipients transplanted between 2001 and 2011 to assess TRAS prevalence and percutaneous transluminal angioplasty (PTA) efficacy. To assess risk factors, we compared children with TRAS with a propensity score-matched cohort of recipients without TRAS.

RESULTS

Of the 216 paediatric patients who were transplanted in the study period, 44 were hypertensive (prevalence 20.3 %) and ten presented with TRAS (prevalence 4.6 %, median age at transplantation 14 years, range 6.78-17.36 years). Hypertensive patients without TRAS were prescribed one to two anti-hypertensive agents, whereas patients with TRAS required one to five medications. In the TRAS group, one recipient presented with vascular complications during surgery, and in three patients the graft had vascular abnormalities. TRAS was detected by Doppler ultrasonography (US) performed due to hypertension in nine of the patients with TRAS, but in the tenth case the TRAS was clinically silent and detected by routine Doppler-US screening. TRAS diagnosis was refined using angio-computed tomography or angio-magnetic resonance imaging. All patients underwent PTA without complications. Significant improvement after PTA was observed in the standard deviation scores for blood pressure [3.2 ± 1.4 (pre-PTA) vs. 1.04 ± 0.8 (post-PTA); p = 0.0006) and graft function [creatinine clearance: 69 ± 17.08 (pre-PTA) vs. 80.7 ± 21.5 ml/min/1.73 m(2) (post-PTA); p = 0.006] We observed no significant differences between the two cohorts for cold ischaemia time, recipient/donor weight ratio, delayed graft function, cytomegalovirus infections and acute rejection episodes.

CONCLUSIONS

Our study reports a low but significant TRAS prevalence among the paediatric patients who were transplanted at our centre in the study period and confirms that PTA is an effective and safe therapeutic option in paediatric renal transplant recipients. Known risk factors do not appear to be related to the development of TRAS.