Hemodialysis arteriovenous fistula maturity: US evaluation

Vascular Access Outcomes Reported in Maintenance Hemodialysis Trials: A Systematic Review

BACKGROUND

Many randomized controlled trials have been performed with the goal of improving outcomes related to hemodialysis vascular access. If the reported outcomes are relevant and measured consistently to allow comparison of interventions across trials, such trials can inform decision making. This study aimed to assess the scope and consistency of vascular access outcomes reported in contemporary hemodialysis trials.

STUDY DESIGN

Systematic review.

SETTING & POPULATION

Adults requiring maintenance hemodialysis.

SELECTION CRITERIA

All randomized controlled trials and trial protocols reporting vascular access outcomes identified from ClinicalTrials.gov, Embase, MEDLINE, and the Cochrane Kidney and Transplant Specialized Register from January 2011 to June 2016.

INTERVENTIONS

Any hemodialysis-related intervention.

OUTCOMES

The frequency and characteristics of vascular access outcome measures were analyzed and classified.

RESULTS

From 168 relevant trials, 1,426 access-related outcome measures were extracted and classified into 23 different outcomes. The 3 most common outcomes were function (136 [81%] trials), infection (63 [38%]), and maturation (31 [18%]). Function was measured in 489 different ways, but most frequently reported as "mean access blood flow (mL/min)" (37 [27%] trials) and "number of thromboses" (30 [22%]). Infection was assessed in 136 different ways, with "number of access-related infections" being the most common measure. Maturation was assessed in 44 different ways at 15 different time points and most commonly characterized by vein diameter and blood flow. Patient-reported outcomes, including pain (19 [11%]) and quality of life (5 [3%]), were reported infrequently. Only a minority of trials used previously standardized outcome definitions.

LIMITATIONS

Restricted sampling frame for feasibility and focus on contemporary trials.

CONCLUSIONS

The reporting of access outcomes in hemodialysis trials is very heterogeneous, with limited patient-reported outcomes and infrequent use of standardized outcome measures. Efforts to standardize outcome reporting for vascular access are critical to optimizing the comparability, reliability, and value of trial evidence to improve outcomes for patients requiring hemodialysis.

Flow Rates at Thirty Days after Construction of Radiocephalic Arteriovenous Fistula Predict Hemodialysis Function

BACKGROUND

Construction of radiocephalic arteriovenous fistula (RC-AVF) results in successful hemodialysis (HD) in approximately 40% of end-stage renal disease patients. We investigated whether RC-AVF flow measured by ultrasound 30 days postoperative predicted successful HD.

METHODS

In this prospective study, color Doppler ultrasound was used to measure cephalic vein outflow volume at 3 forearm sites at 1 and 3 months postoperatively.

RESULTS

Of 45 consecutive patients screened for feasibility of RC-AVF by physical examination and US arterial and vein mapping, 41 were considered suitable for construction of RC-AVF. Mean age was 70 (60-78) years. Of the 41 patients who had a forearm RC-AVF, 25 (61%) proceeded to successful AVF dialysis, 4 (10%) had HD via central venous catheter, and 12 (29%) ceased function within the first 30 days postoperatively. The mean flow at 30 days for patent fistulas was 629 ± 305 ml/min and by the third month had increased to 663 ± 367 mL/min. At 1 month, 8/29 (27.6%) patients had a flow rate <400 mL/min. Two (25%) of these clotted, 2 of 3 with closed revisions went on to HD, and 1 died. Of the 21 patients with a flow rate ≥400 mL/min, 19 (90%) functioned for HD, and 2 (10%) AVF occluded before 1 year, resulting in 17 functioning at 1 year (81% 1-year patency). Sixty-two percent of the low-flow fistulas had successful patency within 1 year.

CONCLUSIONS

An RC-AVF flow rate of ≥400 mL/min in the first month predicted more successful HD than low flow (<400 mL/min) (81% vs. 62%). Without intervention, low flow rates do not improve significantly and maturation is unlikely. We recommend imaging for all patients at 30 days to identify and promptly correct stenosis in those with low flow rates.

Point-of-care ultrasound in the practice of nephrology

Sonography is increasingly being performed by clinicians and has applications throughout the spectrum of nephrology, including acute and chronic renal failure, urinary obstruction, cystic disease, pain, hematuria, transplantation, kidney biopsy, temporary and permanent vascular access, and assessment of fluid status. The skill is relatively easily acquired, expedites patient care, and enhances the practice of nephrology. However, the lack of exposure in most training programs remains a major obstacle.

Comparison of postoperative ultrasound criteria to predict unassisted use of arteriovenous fistulas for hemodialysis

Introduction:

Arteriovenous fistulas (AVF) frequently fail to mature. Postoperative ultrasounds provide objective measurements to predict unassisted AVF use for hemodialysis (unassisted use) and guide interventions to salvage nonmaturing AVFs. The optimal ultrasound criteria to assess AVF maturation are uncertain. We analyzed data from a multicenter, randomized, controlled, clinical trial to compare 2 published ultrasound maturation criteria used to predict unassisted AVF use for hemodialysis.

Methods:

We retrospectively analyzed prospective data on 105 patients undergoing new AVF creation, who underwent standardized postoperative ultrasounds at 6 and 12 weeks to measure AVF diameter and blood flow. Unassisted AVF use was defined as successful cannulation for ≥90 days without requiring prior surgical or percutaneous interventions. Two ultrasound criteria were assessed: (i) National Kidney Foundation (NKF) Kidney Disease Outcome Quality Initiative criteria: AVF outflow vein lumen diameter ≥6 mm and blood flow ≥600 mL/min; and (ii) University of Alabama at Birmingham (UAB) criteria: AVF outflow vein lumen diameter ≥4 mm and blood flow ≥500 mL/min. Performance characteristics were calculated for both criteria.

Results:

Compared to the NKF criteria, the UAB criteria had a higher sensitivity (89 vs.68%), but a lower specificity (42 vs. 70%) for unassisted AVF use. For radiocephalic AVFs, the UAB criteria had higher sensitivity (86 vs. 46%) and lower specificity (58 vs. 83%). For brachiocephalic AVFs, both UAB and NKF had high sensitivity (90 and 80%) but low specificity (21 and 53%), respectively.

Conclusions:

Using the UAB ultrasound criteria would minimize unnecessary early interventions in AVFs likely to mature without an intervention, but would delay interventions in AVFs that are unlikely to mature. The UAB criteria may be preferred in patients receiving a radiocephalic AVF.

Comparison of Complications of Arteriovenous Fistula with Permanent Catheter in Hemodialysis Patients: A Six-month Follow-up

Background:

Arteriovenous fistula (AVF), permanent catheter (PC), and vascular graft are three vascular access types used for hemodialysis procedure. Due to insufficient reliable information on the comparison between AVF and PC, this study was conducted to compare AVF and PC regarding dialysis adequacy.

Materials and Methods:

This prospective study was carried out from March, 2013 to September, 2013. In this study, 76 hemodialysis patients were enrolled and assigned to two unequal groups of AVF and PC. Before and after the dialysis session, blood samples were taken for laboratory examinations and measurement of urea reduction ratio (URR) and Kt/V. The patients were followed up for six months, and then laboratory examinations were repeated.

Results:

Of the 76 hemodialysis patients, 30 had AVF and others PC. During the 6-month follow-up, 24 patients in PC group but only one patient in AVF group showed infection (P = 0.006), while in each group, three cases of thrombosis were seen (P = 0.58); however, catheter dysfunction was seen in 13 patients of PC group but no patients of AVF group (P = 0.004). There was no difference between the two groups in Kt/V and URR at the beginning of the study; however, after six months, Kt/V and URR were greater in AVF group (P < 0.05).

Conclusions:

In addition to some advantages of AVF over PC, such as lower rate of infection and thrombosis, we also found better dialysis adequacy in AVF group. We recommend that AVF be created in all of patients with chronic kidney disease who are candidates for hemodialysis.

Novel use of infrared thermal imaging to predict arteriovenous fistula patency and maturation

OBJECTIVE

The arteriovenous fistula (AVF) is the preferred method of long-term haemodialysis. However, it has been shown to have a substantial rate of maturation failure. The formation of an AVF creates haemodynamic changes to blood flow in the arm with diversion of blood away from the distal circulation into the low pressure venous system, in turn, leading to thermal changes distally. In this study, we aimed to assess the novel use of infrared thermal imaging as a predictor of arteriovenous maturation.

METHODS

A prospective cohort study was conducted on 100 consecutive patients who had AVF formation from December 2015 to June 2016. Infrared thermal imaging was undertaken pre- and post-operatively on the day of surgery to assess thermal changes to the arms and to assess them as predictors of clinical patency and functional maturation.

RESULTS

For clinical patency, infrared thermal imaging was found to have a positive predictive value of 88% and a negative predictive value of 86%. For functional maturation, it was found to have a positive predictive value of 84%, a negative predictive value of 95%. In addition, it was shown to have superiority to the commonly used intra-operative predictor of thrill as well as other independent pre-operative patient factors.

CONCLUSIONS

Infrared thermal imaging has been found to be a very useful tool in accurately predicting fistula patency and maturation.

Imaging in Vascular Access

This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention is indicated. MRI is limited by its cost and the time required for image acquisition that mainly confines it to the realm of research where high resolution is required. CT’s short acquisition times and high resolution make it useful as a problem-solving tool in complex cases, although accessibility can be an issue. All four imaging modalities have advantages and disadvantages that limit their use in this particular patient cohort. Current imaging in VA comprises an integrated approach with each modality providing particular uses dependent on their capabilities. MRI and CT, which currently have limited use, may have increasingly important future roles in complex cases where detailed analysis is required.

Endovascular Proximal Forearm Arteriovenous Fistula for Hemodialysis Access: Results of the Prospective, Multicenter Novel Endovascular Access Trial (NEAT)

BACKGROUND

Hemodialysis arteriovenous fistulas (AVFs) are suboptimally used primarily due to problems with maturation, early thrombosis, and patient nonacceptance. An endovascular approach to fistula creation without open surgery offers another hemodialysis vascular access option.

STUDY DESIGN

Prospective, single-arm, multicenter study (Novel Endovascular Access Trial [NEAT]).

SETTINGS & PARTICIPANTS

Consecutive adult non-dialysis-dependent and dialysis-dependent patients referred for vascular access creation at 9 centers in Canada, Australia, and New Zealand.

INTERVENTION

Using catheter-based endovascular technology and radiofrequency energy, an anastomosis was created between target vessels, resulting in an endovascular AVF (endoAVF).

OUTCOMES

Safety, efficacy, functional usability, and patency end points.

MEASUREMENTS

Safety as percentage of device-related serious adverse events; efficacy as percentage of endoAVFs physiologically suitable (brachial artery flow ≥ 500mL/min, vein diameter ≥ 4mm) for dialysis within 3 months; functional usability of endoAVFs to provide prescribed dialysis via 2-needle cannulation; primary and cumulative endoAVF patencies per standardized definitions.

RESULTS

80 patients were enrolled (20 roll-in and 60 participants in the full analysis set; the latter are reported). EndoAVFs were created in 98% of participants; 8% had a serious procedure-related adverse event (2% device related). 87% were physiologically suitable for dialysis (eg, mean brachial artery flow, 918mL/min; endoAVF vein diameter, 5.2mm [cephalic vein]). EndoAVF functional usability was 64% in participants who received dialysis. 12-month primary and cumulative patencies were 69% and 84%, respectively.

LIMITATIONS

Due to the unique anatomy and vessels used to create endoAVFs, this was a single-arm study without a surgical comparator.

CONCLUSIONS

An endoAVF can be reliably created using a radiofrequency magnetic catheter-based system, without open surgery and with minimal complications. The endoAVF can be successfully used for hemodialysis and demonstrated high 12-month cumulative patencies. It may be a viable alternative option for achieving AVFs for hemodialysis patients in need of vascular access.

Preoperative computer simulation for planning of vascular access surgery in hemodialysis patients

Introduction

The arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis patients. Unfortunately, 20-40% of all constructed AVFs fail to mature (FTM), and are therefore not usable for hemodialysis. AVF maturation importantly depends on postoperative blood volume flow. Predicting patient-specific immediate postoperative flow could therefore support surgical planning. A computational model predicting blood volume flow is available, but the effect of blood flow predictions on the clinical endpoint of maturation (at least 500 mL/min blood volume flow, diameter of the venous cannulation segment ≥4 mm) remains undetermined.

Methods

A multicenter randomized clinical trial will be conducted in which 372 patients will be randomized (1:1 allocation ratio) between conventional healthcare and computational model-aided decision making. All patients are extensively examined using duplex ultrasonography (DUS) during preoperative assessment (12 venous and 11 arterial diameter measurements; 3 arterial volume flow measurements). The computational model will predict patient-specific immediate postoperative blood volume flows based on this DUS examination. Using these predictions, the preferred AVF configuration is recommended for the individual patient (radiocephalic, brachiocephalic, or brachiobasilic). The primary endpoint is FTM rate at six weeks in both groups, secondary endpoints include AVF functionality and patency rates at 6 and 12 months postoperatively.

Trial registration

ClinicalTrials.gov (NCT02453412), and ToetsingOnline.nl (NL51610.068.14).

Patient-related factors influencing patency of autogenous brachiocephalic haemodialysis fistulas

Objective

The objective of this study was to analyse the outcome of autogenous brachiocephalic fistula for dialysis purposes and to determine modifiable and non-modifiable patient-related factors of influence on the patency of a newly created fistula.

Design of study

A single-centre retrospective cohort study with the aim of determining patient-related factors of influence on primary failure, primary, primary assisted and secondary patency of autogenous brachiocephalic fistulas. Seventeen patient-related variables were determined by means of univariate analysis, variables reaching significance were then entered in a multivariate Cox-regression model.

Results

Between October 2005-October 2015, 231 autogenous brachiocephalic fistulas were created in 228 patients. Mean age was 61.3 years (20.3-88.2 years). Patency was calculated using Kaplan-Meier analysis. Primary failure occurred in 38 out of 231 created fistulas (16.5%). The primary, primary assisted and secondary patency rates at six months were 78 ± 3%, 93 ± 2%, and 95 ± 1%, respectively. At 12 months, they were 63 ± 3%, 89 ± 2%, and 92 ± 2%, and at 24 months 47 ± 4%, 84 ± 3%, and 89 ± 2%. The non-modifiable factors, diabetes mellitus and mean cephalic vein diameter were identified as a predictor for failure influencing primary and secondary patency. The preoperative use of anticoagulation was identified as a modifiable factor for failure.

Conclusions

This study identified several non-modifiable and modifiable factors of interest to the clinician deciding on which type of haemodialysis fistula is most suitable for an individual patient. Meticulous preoperative work-up, a surveillance programme, and a dedicated multidisciplinary team can be of great importance in achieving better patency rates.

Sonography of Arteriovenous Fistulas and Grafts

Arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) are the vascular accesses of choice for long-term hemodialysis. Strategies to establish and maintain functioning AVFs and AVGs are essential. In addition to clinical evaluation, ultrasound plays a critical role in the evaluation and maintenance of AVFs and AVGs. AVFs have a high rate of failure to mature which can be reliably diagnosed with ultrasound. Treatable etiologies of the failure to mature can often be diagnosed with ultrasound. Causes of secondary AVG failure can also be diagnosed with ultrasound and treated. AVGs have a relatively short functional life expectancy due to a high rate of AVG thrombosis. Ultrasound is a safe, noninvasive way to diagnose vascular stenosis in both AVFs and AVGs prior to thrombosis, potentially saving the access. Routine surveillance ultrasound of asymptomatic AVFs and AVGs is controversial with conflicting studies on its benefit. Routine surveillance ultrasound of AVFs and AVGs is not common practice.

Optimal timing for vascular access creation

Many guidelines recommend that end-stage renal disease (ESRD) patients should have a permanent vascular access, preferably an autologous arteriovenous fistula (AVF), at the start of renal replacement therapy. Nevertheless, a large proportion of patients still start hemodialysis with a central venous catheter (CVC). On the other hand, there are increasing numbers of patients in whom an AVF has been created, but who never actually end up on dialysis, as well as a substantial number of patients in whom creation of a vascular access has been attempted unsuccessfully.To improve this situation, timely exploration to assess suitability for and creation of preemptive AVF should be promoted. Decision to construct an AVF should depend on the likelihood and rate of progression to ESRD. For this goal, some reliable prediction models are available. Also, the likelihood that such an attempt will result in a successful outcome should be taken into account, but suitable validated models to accurately make such estimates are lacking. Next to patient-specific factors, some local conditions such as easy access to a vascular surgeon should also be incorporated in the decision-making process between the nephrology team and the patient.

Improvement of radiocephalic fistula maturation: rationale and design of the Liposomal Prednisolone to Improve Hemodialysis Fistula Maturation (LIPMAT) study - a randomized controlled trial

BACKGROUND

Non-maturation is a frequent complication of radiocephalic arteriovenous fistulas (RCAVF). In an animal model, liposomal prednisolone improved maturation of experimental fistulas. The Liposomal Prednisolone to Improve Hemodialysis Fistula Maturation (LIPMAT) study investigates if liposomal prednisolone improves RCAVF maturation.

METHODS AND RESULTS

The LIPMAT study is an investigator-initiated, multicenter, double-blinded, placebo-controlled randomized controlled trial with 1:1 randomization to liposomal prednisolone or placebo. Eighty patients receiving an RCAVF will be included. The primary outcome is the cephalic vein diameter six weeks after surgery, measured by ultrasound. The LIPMAT study started in May 2016. Enrollment is expected to be completed by the end of 2017.

CONCLUSIONS

The LIPMAT study is the first to evaluate the efficacy of liposomal prednisolone to enhance RCAVF maturation.

Optiflow anastomotic device for hemodialysis vascular access creation

The need to have consistent methods and consistent technique to optimize hemodialysis outcomes is behind the concept of the Optiflow™ device. This device was created to allow for consistency in size of the arterial anastomosis and consistency in angle of the vein to the artery at the anastomosis. Early data suggest that allowing these two technical entities can improve outcomes in regards to flow and maturity in arteriovenous fistula creation. This article is a summary of early data that demonstrate the impact the Optiflow device on brachial cephalic fistulas.

Early use of autogenous arteriovenous fistula in patients with urgent hemodialysis

PURPOSE

This study was designed to evaluate the long-term patency rate and complications associated with early use of the autogenous forearm arteriovenous fistula (AFAVF) in patients needing urgent hemodialysis.

METHODS

The clinical data of all patients undergoing AFAVFs for hemodialysis access between June 1996 and June 2016 were retrospectively evaluated. The primary and secondary patencies were estimated using the life table method.

RESULTS

A total of 104 AFAVFs were created for 102 patients. All patients had entered hemodialysis when fistulas were constructed. The mean time to the first cannulation of the AFAVF was 17.33 ± 4.60 (5-27 days). Four AFAVFs (3.8%) became occluded within 30 days of creation of the access, and five AFAVFs (4.8%) had hematomas after cannulation. There were no cases of infection of the wound or steal syndrome or prolonged arm edema. The primary patency rate was 77.81% at 1 year, 73.05% at 2 years, 64.64% at 3 years, 60.75% at 5 years and 47.48% at 10 years. The secondary patency rate was 96.78% at 1 year, 95.18% at 5 years and 85.81% at 10 years.

CONCLUSIONS

In this study, the patency rates following the early use of the AFAVFs were not inferior to the previously reported patency rates in the literature. For patients entering hemodialysis with an inserted central catheter, the early use of the AFAVFs decreases the complications associated with catheters.

Arteriovenous Grafts: Much Maligned But in Need of Reconsideration?

There are substantial variations in arteriovenous fistula (AVF) use among hemodialysis patients in different countries, in different regions of the U.S., and even in different hemodialysis units within a single metropolitan area. These variations persist after adjustment for patient demographics and comorbidities, suggesting that practice patterns play a major role in determining the frequency of AVF use. These observations led to vascular access guidelines urging nephrologists and surgeons to increase AVF creation in patients with chronic kidney disease. Over the past 20 years, as clinicians have adopted these guidelines, the prevalence of AVF use in hemodialysis patients has increased substantially. At the same time, clinicians have recognized important limitations of an unwavering "Fistula First" approach. First, a substantial proportion of AVFs fail to mature even when routine preoperative vascular mapping is used, leading to prolonged catheter dependence. Second, certain patient subgroups are at high risk for AVF nonmaturation. Third, nonmaturing AVFs frequently require interventions to promote their maturation. Fourth, AVFs that require such interventions have shortened cumulative patency. Fifth, arteriovenous grafts (AVG) have several advantages over AVFs, including lower primary failure rates, fewer interventions prior to successful cannulation, and shorter duration of catheter dependence with its associated risk of bacteremia. All these observations have led nephrologists to propose an individualized approach to vascular access, with AVG being preferred in patients who initiate hemodialysis with a catheter, particularly if they are at high risk for AVF nonmaturation and have a relatively short life expectancy.

Native arteriovenous fistula placement in three patients after implantation of a left ventricular assist device with non-pulsatile blood flow

Patients with left ventricular assist device have an increased risk for postoperative acute kidney injury and long-term requirement of dialysis. As a chronic access for dialysis, native arteriovenous fistulae are uncommon options due to suspected maturation failure. We present three patients who received successful arteriovenous fistulae placement after left ventricular assist device implantation with assisted long term patency.

Arteriovenous fistula patency in the 3 years following vonapanitase and placebo treatment

OBJECTIVE

This study explored the long-term outcomes of arteriovenous fistulas treated with vonapanitase (recombinant human elastase) at the time of surgical creation.

METHODS

This was a randomized, double-blind, placebo-controlled trial of 151 patients undergoing radiocephalic or brachiocephalic arteriovenous fistula creation who were randomized equally to placebo, vonapanitase 10 μg, or vonapanitase 30 μg. The results after 1 year of follow-up were previously reported. The current analysis occurred when the last patient treated was observed for 3 years. For the current analysis, the primary end point was primary patency; the secondary end points included secondary patency, use of the fistula for hemodialysis, and rate of procedures to restore or to maintain patency.

RESULTS

There was no significant difference in the risk of primary patency loss with vonapanitase 10 μg or 30 μg vs placebo. When seven initial patency loss events related to cephalic arch and central vein balloon angioplasty were excluded, the risk of patency loss was reduced with vonapanitase overall (hazard ratio [HR], 0.63; P = .049) and 30 μg (HR, 0.51; P = .03). In patients with radiocephalic fistulas (n = 67), the risks of primary and secondary patency loss were reduced with 30 μg (HR, 0.37 [P = .02] and 0.24 [P = .046], respectively). The rate of procedures to restore or to maintain fistula patency was reduced with 30 μg vs placebo (0.23 vs 0.72 procedure days/patient/year; P = .03) and also reduced in patients with radiocephalic fistulas with 30 μg vs placebo (0.17 vs 0.85 procedure days/patient/year; P = .048).

CONCLUSIONS

In this study, vonapanitase did not significantly improve primary patency in the primary analysis but did significantly improve primary patency in an analysis that excluded patency loss due to cephalic arch and central vein balloon angioplasty. In patients with radiocephalic fistulas, 30 μg significantly improved primary and secondary patency. Vonapanitase 30 μg decreased the rate of procedures to restore or to maintain patency in the analysis that included all patients and in the subset with radiocephalic fistulas.

Association between Preoperative Vascular Function and Postoperative Arteriovenous Fistula Development

Arteriovenous fistula (AVF) maturation failure is the primary cause of dialysis vascular access dysfunction. To evaluate whether preoperative vascular functional properties predict postoperative AVF measurements, patients enrolled in the Hemodialysis Fistula Maturation Study underwent up to five preoperative vascular function tests (VFTs): flow-mediated dilation (FMD), nitroglycerin-mediated dilation (NMD), carotid-femoral pulse wave velocity, carotid-radial pulse wave velocity, and venous occlusion plethysmography. We used mixed effects multiple regression analyses to relate each preoperative VFT to ultrasound measurements of AVF blood flow rate and venous diameter at 1 day, 2 weeks, and 6 weeks after AVF placement. After controlling for AVF location, preoperative ultrasound measurements, and demographic factors (age, sex, race, and dialysis status), greater NMD associated with greater 6-week AVF blood flow rate and AVF diameter (per absolute 10% difference in NMD: change in blood flow rate =14.0%; 95% confidence interval [95% CI], 3.7% to 25.3%; P<0.01; change in diameter =0.45 mm; 95% CI, 0.25 to 0.65 mm; P<0.001). Greater FMD also associated with greater increases in 6-week AVF blood flow rate and AVF diameter (per absolute 10% difference in FMD: change in blood flow rate =11.6%; 95% CI, 0.6% to 23.9%; P=0.04; change in diameter =0.31 mm; 95% CI, 0.05 to 0.57 mm; P=0.02). None of the remaining VFT parameters exhibited consistent statistically significant relationships with both postoperative AVF blood flow rate and diameter. In conclusion, preoperative NMD and FMD positively associated with changes in 6-week AVF blood flow rate and diameter, suggesting that native functional arterial properties affect AVF development.

A Prospective, Randomized Trial of Routine Duplex Ultrasound Surveillance on Arteriovenous Fistula Maturation

BACKGROUND AND OBJECTIVES

Use of arteriovenous fistulas, the most preferred type of access for hemodialysis, is limited by their high maturation failure rate. The aim of this study was to assess whether aggressive surveillance with routine duplex ultrasound and intervention can decrease the maturation failure rate of arteriovenous fistulas.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a single-center, parallel-group, randomized, controlled trial of patients undergoing autogenous arteriovenous fistula. Patients were randomly assigned (1:1) to either the routine duplex or selective duplex group. In the routine duplex group, duplex ultrasound and physical examination were performed 2, 4, and 8 weeks postoperatively. In the selective duplex group, duplex examination was performed only when physical examination detected an abnormality. The primary end point was the maturation failure rate 8 weeks after fistula creation. Maturation failure was defined as the inability to achieve clinical maturation (i.e., a successful first use) and failure to achieve sonographic maturation (fistula flow >500 ml/min and diameter >6 mm) within 8 weeks.

RESULTS

Between June 14, 2012, and June 25, 2014, 150 patients were enrolled (75 patients in each group), and 118 of those were included in the final analysis. The maturation failure rate was lower in the routine duplex group (8 of 59; 13.6%) than in the selective duplex group (15 of 59; 25.4%), but the difference was not statistically significant (odds ratio, 0.46; 95% confidence interval, 0.18 to 1.19; P=0.10). Factors associated with maturation failure were women (odds ratio, 3.84; 95% confidence interval, 1.05 to 14.06; P=0.04), coronary artery disease (odds ratio, 6.36; 95% confidence interval, 1.62 to 24.95; P<0.01), diabetes (odds ratio, 6.10; 95% confidence interval, 1.76 to 21.19; P<0.01), and the preoperative cephalic vein diameter (odds ratio, 0.30; 95% confidence interval, 0.13 to 0.71; P<0.01).

CONCLUSIONS

Postoperative routine duplex surveillance failed to prove superiority compared with selective duplex after physical examination for reducing arteriovenous fistula maturation failure. However, the wide 95% confidence interval for the effect of intervention precludes a firm conclusion that routine duplex surveillance was not beneficial.

Predictors of Initiation for Predialysis Arteriovenous Fistula

BACKGROUND AND OBJECTIVES

The optimal timing of predialysis arteriovenous fistula surgery remains uncertain. We evaluated factors associated with hemodialysis initiation in patients undergoing predialysis arteriovenous fistula surgery and derived a model to predict future initiation of dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our study retrospectively identified 308 patients undergoing predialysis arteriovenous fistula creation at a large medical center in 2006-2012 to determine whether they initiated hemodialysis. Multiple variable logistic regression analyzed which demographic and clinical factors predicted initiation of dialysis within 2 years of arteriovenous fistula surgery. A receiver operating characteristic area under the curve was used to quantify the predictive value of preoperative factors on the likelihood of initiating hemodialysis within 2 years.

RESULTS

Overall, hemodialysis was initiated within 6 months, 1 year, and 2 years in 119 (39%), 175 (57%), and 211 (68%) patients, respectively. Using multiple variable logistic regression, four factors were associated with hemodialysis initiation at 2 years: eGFR at access surgery (odds ratio, 0.45; 95% confidence interval, 0.31 to 0.64 per 5 ml/min per 1.73 m2; P<0.001), diabetes (odds ratio, 2.51; 95% confidence interval, 1.22 to 5.15; P=0.003), GFR trajectory (odds ratio, 1.54; 95% confidence interval, 1.09 to 2.17 per 3 ml/min per 1.73 m2 per year; P=0.01), and spot urine protein-to-creatinine ratio (odds ratio, 1.39; 95% confidence interval, 1.14 to 1.71 per 1 U; P<0.001). eGFR alone had a moderate predictive value for dialysis initiation (area under the curve =0.69; 95% confidence interval, 0.63 to 0.76; P<0.001), whereas the full model had a higher predictive value (area under the curve =0.83; 95% confidence interval, 0.77 to 0.88; P<0.001).

CONCLUSIONS

The likelihood of initiating hemodialysis within 2 years of predialysis arteriovenous fistula surgery is associated with eGFR at access surgery, diabetes, GFR trajectory, and magnitude of proteinuria. The combined use of all four variables improves the ability to predict future hemodialysis compared with the use of eGFR alone.

Arteriovenous Vascular Access Selection and Evaluation

When making decisions regarding vascular access creation, the clinician and vascular access team must evaluate each patient individually with consideration of life expectancy, timelines for dialysis start, risks and benefits of access creation, referral wait times, as well as the risk for access complications. The role of the multidisciplinary team in facilitating access choice is reviewed, as well as the clinical evaluation of the patient.

Very low protein diets supplemented with keto-analogues in ESRD predialysis patients and its effect on vascular stiffness and AVF Maturation

Background

Native arteriovenous fistula (AVF) is the most appropriate type of vascular access for chronic dialysis. Its patency rates depend on vascular wall characteristics. Ketoacid analogues of essential amino acids (KA/EAA) are prescribed in end-stage renal disease (ESRD) pre-dialysis patients to lower toxic metabolic products generation and improve nutritional status. We hypothesized that very-low protein diet (VLPD) supplemented with KA/EAA may influence arterial wall stiffness and affect AVF maturation rates and duration in pre-dialysis ESRD patients.

Methods

In a prospective, cohort, 3 years study we enrolled 67 consecutive non-diabetic early referral ESRD patients that underwent AVF creation in our hospital. Patients were divided in two groups based on their regimen 12 months prior to surgery: a VLPD supplemented with KA/EAA study group versus a low protein diet non-KA/EAA-supplemented control group. For each patient we performed serum analysis for the parameters of bone mineral disease, inflammation and nutritional status, one pulse wave velocity (PWV) measurement and one Doppler ultrasound (US) determination prior the surgery, followed by consequent Doppler US assessments at 4, 6, 8 and 12 weeks after it. Rates and duration of mature AVF achievement were noted. We used logistic regression to analyze the association between AVF maturation and KA/EAA administration, by comparing rates and durations between groups, unadjusted and adjusted for systolic blood pressure, C-reactive protein, PWV, phosphorus values. All parameters in the logistic model were transformed in binary variables. A p-value < α = 0.05 was considered significant; data were processed using SPSS 16 software and Excel.

Results

In the study group (n = 28, aged 57 ± 12.35, 13 females) we registered better serum phosphate (p = 0.022) and C-reactive protein control (p = 0.021), lower PWV (p = 0.007) and a higher percent of AVF creation success (33.3 % versus 17.8 %, p < 0.05). AVF maturation duration was lower in study group (5.91 versus 7.15 weeks, p < 0.001).

Conclusions

VLPD supplemented with KA/EAA appear to improve the native AVF primary outcome, decreasing the initial vascular stiffness, possible by preserving vascular wall quality in CKD patients through a better serum phosphate levels control and the limitation of inflammatory response.

Is Brachial Artery Blood Flow Measured by Sonography During Early Postoperative Periods Predictive of Arteriovenous Fistula Failure in Hemodialysis Patients?

OBJECTIVES

The aim of our study was to determine a brachial artery blood flow level measured by sonography during early postoperative periods that is predictive of arteriovenous fistula failure in hemodialysis patients.

METHODS

Doppler sonography was used to estimate the blood flow in the brachial artery of 103 patients at 1 and 14 days after arteriovenous fistula creation. The performance of brachial artery blood flow during early postoperative periods for predicting fistula failure was evaluated, and optimal cutoff values were determined.

RESULTS

During a 6-month follow-up, 85 fistulas were classified as mature, and 18 were classified as failures. The reproducibility of blood flow measurements in the brachial artery was good (intraclass correlation coefficient, 0.912). The blood flow in the failure group was significantly lower than that in the mature group at both 1 and 14 days after fistula creation (P < .05). During the first 2 postoperative weeks, the blood flow increased by 40.7% in the failure group versus 78.3% in the mature group. The areas under the receiver operating characteristic curves of brachial artery blood flow for predicting failure were 0.77 (95% confidence interval, 0.66-0.87; optimal cutoff value, 310 mL/min)at 1 day and 0.91 (95% confidence interval, 0.83-0.99; 413 mL/min) at 14 days after fistula creation.

CONCLUSIONS

Brachial artery blood flow measured by sonography during early postoperative periods may be predictive of forearm fistula failure. Blood flow of less than 310 mL/min at 1 day and 413 mL/min at 14 days after fistula creation may indicate a risk of failure to mature.

New Insights into Dialysis Vascular Access: What Is the Optimal Vascular Access Type and Timing of Access Creation in CKD and Dialysis Patients?

Optimal vascular access planning begins when the patient is in the predialysis stages of CKD. The choice of optimal vascular access for an individual patient and determining timing of access creation are dependent on a multitude of factors that can vary widely with each patient, including demographics, comorbidities, anatomy, and personal preferences. It is important to consider every patient's ESRD life plan (hence, their overall dialysis access life plan for every vascular access creation or placement). Optimal access type and timing of access creation are also influenced by factors external to the patient, such as surgeon experience and processes of care. In this review, we will discuss the key determinants in optimal access type and timing of access creation for upper extremity arteriovenous fistulas and grafts.

Access-related hand ischemia and the Hemodialysis Fistula Maturation Study

OBJECTIVE

Access-related hand ischemia (ARHI) is a major complication after hemodialysis access construction. This study was designed to prospectively describe its incidence, predictors, interventions, and associated access maturation.

METHODS

The Hemodialysis Fistula Maturation Study is a multicenter prospective cohort study designed to identify predictors of autogenous arteriovenous access (arteriovenous fistula [AVF]) maturation. Symptoms and interventions for ARHI were documented, and participants who received interventions for ARHI were compared with other participants using a nested case-control design. Associations of ARHI with clinical, ultrasound, vascular function, and vein histologic variables were each individually evaluated using conditional logistic regression; the association with maturation was assessed by relative risk, Pearson χ(2) test, and multiple logistic regression.

RESULTS

The study cohort included 602 participants with median follow-up of 2.1 years (10th-90th percentiles, 0.7-3.5 years). Mean age was 55.1 ± 13.4 (standard deviation) years; the majority were male (70%), white (47%), diabetic (59%), smokers (55%), and on dialysis (64%) and underwent an upper arm AVF (76%). Symptoms of ARHI occurred in 45 (7%) participants, and intervention was required in 26 (4%). Interventions included distal revascularization with interval ligation (13), ligation (7), banding (4), revision using distal inflow (1), and proximalization of arterial inflow (1). Interventions were performed ≤7 days after AVF creation in 4 participants (15%), between 8 and 30 days in 6 (23%), and >30 days in 16 (63%). Female gender (odds ratio, 3.17; 95% confidence interval, 1.27-7.91; P = .013), diabetes (13.62 [1.81-102.4]; P = .011), coronary artery disease (2.60 [1.03-6.58]; P = .044), higher preoperative venous capacitance (per %/10 mm Hg, 2.76 [1.07-6.52]; P = .021), and maximum venous outflow slope (per [mL/100 mL/min]/10 mm Hg, 1.13 [1.03-1.25]; P = .011) were significantly associated with interventions; a lower carotid-femoral pulse wave velocity and the outflow vein diameter in the early postoperative period (days 0-3) approached significance (P < .10). Intervention for ARHI was not associated with AVF maturation failure (unadjusted risk ratio, 1.18 [0.69-2.04], P = .56; adjusted odds ratio, 0.97 [0.41-2.31], P = .95).

CONCLUSIONS

Remedial intervention for ARHI after AVF construction is uncommon. Diabetes, female gender, capacitant outflow veins, and coronary artery disease are all associated with an increased risk of intervention. These higher risk patients should be counseled preoperatively, their operative plans should be designed to reduce the risk of hand ischemia, and they should be observed closely.

Echo Color Doppler Ultrasound: A Valuable Diagnostic Tool in the Assessment of Arteriovenous Fistula in Hemodialysis Patients

A functioning vascular access is a critical requirement to improve the quality of life in hemodialysis patients, so monitoring and surveillance of vascular access play key roles in identifying all dysfunctions and reducing the huge economic cost as well as adequacy of dialysis.

In our five-year experience, a study protocol has been used and improved with the help of ultrasonography. Doppler ultrasound is an excellent and sensitive modality for hemodialysis access evaluation, one of techniques employed for arteriovenous fistulae (AVF) study, not only as a pre-operative tool, but also in post-operative monitoring of AVF maturation. In addition, the current guidelines recommend AVF surveillance by access blood flow measurement and the correction of hemodynamic stenosis in order to prolong access survival. Doppler ultrasound is readily available, directly used by nephrologists, non-invasive, safe, inexpensive, reproducible, although it requires more clinical skill and time to perform and proper equipment. Ultrasonography imaging can substantially reduce the number of subsequent invasive angiographic procedures. In our opinion, Doppler ultrasound should have a crucial place in the interdisciplinary cooperation in AVF monitoring and it should be included as part of an integrated vascular access management program.

The association of endothelial progenitor cell markers with arteriovenous fistula maturation in hemodialysis patients

AIMS

Arteriovenous fistula (AVF) failure is one of the most important clinical problems in end-stage renal disease. Endothelial progenitor cells (EPCs) have a role on vascular angiogenesis and endothelialization. We aimed to investigate the association markers of EPCs on AVF maturation by measuring the surface expressions of CD34, CD309 and CD133 on the monocytes.

METHODS

This prospective observational study was conducted in 54 voluntary patients with end-stage renal disease who were admitted for their first renal replacement therapy and were available for AVF creation. Venography was performed in all patients before AVF creation. Six patients were excluded due to inadequate veins after venographic imaging, and also seven patients were excluded due to postoperative thrombosis. The blood samples were analyzed a day before the fistula operation, and the expressions of CD34, CD133 and CD309 on the surface of monocytes were measured.

RESULTS

Patients were divided into two groups after the evaluation of AVF maturation, as the mature group and the failure group. The CD309 expression level on the monocytes was 338.00 (35.00-479.00) in the mature group; however, it was 36.00 (5.50-237.00) (p 0.031) in the failure group. Multiple logistic regression analyses showed that both BMI and the mean fluorescence intensity level of CD309 expression on monocytes independently predicted AVF maturation.

CONCLUSIONS

The presence of DM and increased BMI negatively correlated with AVF maturation. High intensity of CD309 expression on monocytes was observed in patients with successful AVF maturation.

Importance of monitoring and treatment of failed maturation in radiocephalic arteriovenous fistula in predialysis: Role of ultrasound

The aim of the study was to analyse outcomes of AVF-RC in predialysis stage in which a clinical and radiological follow up of its maturation had been done and primary failure had been treated.

MATERIAL AND METHODS

We studied 127 RC-AVF in 117 predialysis patients. All cases had a preoperative map. The RC-AVF was considered mature if it had a brachial artery flow ≥500ml/min and a cephalic vein diameter of ≥4mm. Primary failure was treated radiologically or surgically depending on the type of lesion. Fifty-eight patients started dialysis at the time of the study.

RESULTS

In 106 RC-AVF without thrombosis, 72 (68%) were mature and 34 (32%) were immature. A total of 97% of the immature had at least one lesion, and the most common site was the post-anastomotic vein. Lesions were found in 31% of mature RC-AVF, and 18% of patients required treatment. Radiological treatment was the most frequent for maturation failure. After 6 months, primary and secondary patency were 59% and 78%, while after 12 months they were 48% and 77%, respectively. The 80% of patients started dialysis with a distal AVF (76% RC-AVF and 4% ulnar basilic). None of the patients with treated immature RC-AVF started dialysis with CVC, while 78% of the patients started with said AVF.

CONCLUSION

Ultrasonography for monitoring maturation provides advantages over clinical monitoring. With our management of RC-AVF in predialysis, 80% of patients start dialysis with an adequate distal AVF.

Predicting Factors for Successful Maturation of Autogenous Haemodialysis Fistulas After Salvage Percutaneous Transluminal Angioplasty in Diabetic Nephropathy: A Study on Follow-Up Doppler Ultrasonography

BACKGROUND

Maturation failure of autogenous arteriovenous fistula (aAVF) has been increasing after surgical procedures and the salvage percutaneous transluminal angioplasty (sPTA) for immature aAVF has been identified as an effective treatment modality.

OBJECTIVES

The aim of this study was to identify factors predicting successful aAVF maturation and to determine positive technical aspects of sPTA.

PATIENTS AND METHODS

We retrospectively reviewed medical records and radiological images of 59 patients who had undergone sPTA for non-maturing aAVFs. We analysed images from pre-surgical mapping Doppler ultrasonography, angiography, and angioplasty and follow-up Doppler ultrasonography performed within two weeks after sPTA. We assessed the following factors, for their ability to predict successful aAVF maturation: 1) patient factors (age; sex; co-morbidities; and aAVF age, side and type); 2) vessel factors (cephalic vein diameter and depth, presence of accessory veins, and pre- and postoperative radial artery disease); 3) lesion factors (stenosis number, location and severity); and 4) technical factors (presence of residual stenosis and anatomic success ratio (ASR) on follow-up Doppler ultrasonography).

RESULTS

The technical and clinical success rates were both 94.9% (56/59); the mean ASR was 0.84. An ASR of ≥ 0.7 and no significant residual stenosis (< 30%) (both P < 0.001) on two-week follow-up Doppler ultrasonography predicted successful aAVF maturation.

CONCLUSION

For more precise prediction of successful aAVF maturation after sPTA, short-term follow-up Doppler ultrasonography (< 2 weeks) was useful. If the ASR was < 0.7 or if residual stenosis was ≥ 30%, immediate repeat sPTA is recommended.

Clinical utility of far-infrared therapy for improvement of vascular access blood flow and pain control in hemodialysis patients

Background

Maintenance of a well-functioning vascular access and minimal needling pain are important goals for achieving adequate dialysis and improving the quality of life in hemodialysis (HD) patients. Far-infrared (FIR) therapy may improve endothelial function and increase access blood flow (Qa) and patency in HD patients. The aim of this study was to evaluate effects of FIR therapy on Qa and patency, and needling pain in HD patients.

Methods

This prospective clinical trial enrolled 25 outpatients who maintained HD with arteriovenous fistula. The other 25 patients were matched as control with age, sex, and diabetes. FIR therapy was administered for 40 minutes during HD 3 times/wk and continued for 12 months. The Qa was measured by the ultrasound dilution method, whereas pain was measured by a numeric rating scale at baseline, then once per month.

Results

One patient was transferred to another facility, and 7 patients stopped FIR therapy because of an increased body temperature and discomfort. FIR therapy improved the needling pain score from 4 to 2 after 1 year. FIR therapy increased the Qa by 3 months and maintained this change until 1 year, whereas control patients showed the decrease in Qa. The 1-year unassisted patency with FIR therapy was not significantly different from control.

Conclusion

FIR therapy improved needling pain. Although FIR therapy improved Qa, the unassisted patency was not different compared with the control. A larger and multicenter study is needed to evaluate the effect of FIR therapy.

Arteriovenous Fistula Development in the First 6 Weeks after Creation

PURPOSE

To assess the anatomic development of native arteriovenous fistula (AVF) during the first 6 weeks after creation by using ultrasonographic (US) measurements in a multicenter hemodialysis fistula maturation study.

MATERIALS AND METHODS

Each institutional review board approved the prospective study protocol, and written informed consent was obtained. Six hundred and two participants (180 women and 422 men, 459 with upper-arm AVF and 143 with forearm AVF) from seven clinical centers underwent preoperative artery and vein US mapping. AVF draining vein diameter and blood flow rate were assessed postoperatively after 1 day, 2 weeks, and 6 weeks. Relationships among US measurements were summarized after using multiple imputation for missing measurements.

RESULTS

In 55% of forearm AVFs (68 of 124) and 83% of upper-arm AVFs (341 of 411) in surviving patients without thrombosis or AVF intervention prior to 6 weeks, at least 50% of their 6-week blood flow rate measurement was achieved at 1 day. Among surviving patients without thrombosis or AVF intervention prior to week 2, 70% with upper-arm AVFs (302 of 433) and 77% with forearm AVFs (99 of 128) maintained at least 85% of their week 2 flow rate at week 6. Mean AVF diameters of at least 0.40 cm were seen in 85% (389 of 459), 91% (419 of 459), and 87% (401 of 459) of upper-arm AVFs and in 40% (58 of 143), 73% (104 of 143), and 77% (110 of 143) of forearm AVFs at 1 day, 2 weeks, and 6 weeks, respectively. One-day and 2-week AVF flow rates and diameters were used to predict 6-week levels, with 2-week prediction of 6-week measures more accurate than those of 1 day (flow rates, R(2) = 0.47 and 0.61, respectively; diameters, R(2) = 0.49 and 0.82, respectively).

CONCLUSION

AVF blood flow rate at 1 day is usually more than 50% of the 6-week blood flow rate. Two-week measurements are more predictive of 6-week diameter and blood flow than those of 1 day. US measurements at 2 weeks may be of value in the early identification of fistulas that are unlikely to develop optimally.

U-vein compressor improves early haemodynamic outcomes in radiocephalic arterio-venous fistulae in under 2-mm superficial veins

AIM

In this study, we sought to determine the early postoperative results of arterio-venous fistulae (AVF) created by U-vein compressors with veins between 1.5 and 2 mm in size.

METHODS

Pre-operative venous mapping was done. The fistula tract was marked at 0-, 4-, 8- and 12-cm points; 0 cm was the estimated point where the anastomosis would be done. With Doppler ultrasonography, transverse diameters in the estimated fistula tract were measured at the 0-, 4-, 8- and 12-cm points. A superficial vein that would be used as the fistula tract was dilated using U-vein compressors. In the first postoperative hour, the flow in the anastomosis, and the transverse diameter of the fistula tract at the 0-, 4-, 8- and 12-cm points were measured by Doppler ultrasonography.

RESULTS

Forty patients were included in the study. U-vein compressors were used for 20 patients. Postoperative expansion of vein diameters and postoperative flow velocities were found to be statistically significantly different in patients where a U-vein compressor had been used (p < 0.001).

CONCLUSION

We present a technique to dilate veins that are between 1.5 and 2 mm in diameter, which are generally accepted as poor vessels to create radiocephalic arteriovenous fistulae.

Autotransplantation of parathyroid grafts into the tibialis anterior muscle after parathyroidectomy: a novel autotransplantation site

Background

Surgical management of renal secondary hyperparathyroidism (sHPT) is varying. Total parathyroidectomy with heterotopic autotransplantation (TPTX + AT) is one of the standard surgical procedures in sHPT, but there is no consensus about the optimal site for graft insertion. At the surgical department of the University Hospital of Heidelberg we prefer the autotransplantation into the tibialis anterior muscle. The aim of this study was to assess the long-term function of the auto-transplanted parathyroid tissue in this type of surgical procedure.

Methods

The function of the autograft of 42 patients was assessed 8.2 ± 2.5 years after surgery, using a modified Casanova-test of the leg bearing the parathyroid tissue. Ischemic blockage was induced by tourniquet and the levels of parathyroid hormone (PTH) were assessed during the test.

Results

At the point of assessment, the ischemic blockage led to a significant reduction in the concentration of PTH (≥50 % of the baseline value) in 19 patients (45 %) indicating well-functioning autografts. In 11 patients (26 %), ischemic blockage did not cause any change in the concentration of PTH (≤20 % of the baseline value), indicating functioning residual parathyroid tissue from another site. The source of PTH production was classified as unidentifiable in five patients (12 %). Two patients had developed graft-dependent recurrent HPT (5 %) without therapeutic consequences and three patients suffered from persistent symptomatic hypoparathyroidism (7 %).

Conclusions

These results indicate that TPTX + AT into the tibialis anterior muscle is a successful surgical treatment for renal HPT and that the modified Casanova-test is a suitable diagnostic tool for autografts function.

Preoperative vascular access evaluation for haemodialysis patients

BACKGROUND

Haemodialysis treatment requires reliable vascular access. Optimal access is provided via functional arteriovenous fistula (fistula), which compared with other forms of vascular access, provides superior long-term patency, requires few interventions, has low thrombosis and infection rates and cost. However, it has been estimated that between 20% and 60% of fistulas never mature sufficiently to enable haemodialysis treatment. Mapping blood vessels using imaging technologies before surgery may identify vessels that are most suitable for fistula creation.

OBJECTIVES

We compared the effect of conducting routine radiological imaging evaluation for vascular access creation preoperatively with standard care without routine preoperative vessel imaging on fistula creation and use.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 14 April 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that enrolled adult participants (aged ≥ 18 years) with chronic or end-stage kidney disease (ESKD) who needed fistulas (both before dialysis and after dialysis initiation) that compared fistula maturation rates relating to use of imaging technologies to map blood vessels before fistula surgery with standard care (no imaging).

DATA COLLECTION AND ANALYSIS

Two authors assessed study quality and extracted data. Dichotomous outcomes, including fistula creation, maturation and need for catheters at dialysis initiation, were expressed as risk ratios (RR) with 95% confidence intervals (CI). Continuous outcomes, such as numbers of interventions required to maintain patency, were expressed as mean differences (MD). We used the random-effects model to measure mean effects.

MAIN RESULTS

Four studies enrolling 450 participants met our inclusion criteria. Overall risk of bias was judged to be low in one study, unclear in two, and high in one.There was no significant differences in the number of fistulas that were successfully created (4 studies, 433 patients: RR 1.06, 95% CI 0.95 to 1.28; I² = 76%); the number of fistulas that matured at six months (3 studies, 356 participants: RR 1.11, 95% CI 0.98 to 1.25; I² = 0%); number of fistulas that were used successfully for dialysis (2 studies, 286 participants: RR 1.12, 95% CI 0.99 to 1.28; I² = 0%); the number of patients initiating dialysis with a catheter (1 study, 214 patients: RR 0.66, 95% CI 0.42 to 1.04); and in the rate of interventions required to maintain patency (1 study, 70 patients: MD 14.70 interventions/1000 patient-days, 95% CI -7.51 to 36.91) between the use of preoperative imaging technologies compared with standard care (no imaging).

AUTHORS' CONCLUSIONS

Based on four small studies, preoperative vessel imaging did not improve fistula outcomes compared with standard care. Adequately powered prospective studies are required to fully answer this question.

Series of Noncontrast Time-of-Flight Magnetic Resonance Angiographies to Identify Problems with Arteriovenous Fistula Maturation

BACKGROUND

Successful maturation of arteriovenous fistulas (AVFs) remains a challenge for those managing patients with end-stage renal disease. Time-of-flight magnetic resonance angiography (TOF-MR) can be used to evaluate AVFs without the risk of radiation exposure, intravenous contrast, or reliance on the operator-dependent modality of color Doppler ultrasonography (CDUS). The objective of our study was to assess the utility of TOF-MR in the evaluation of nonmaturing AVFs and to identify the best clinical situations to use this technology.

METHODS

Consecutive patients with abnormal findings on CDUS or physical examination after AVF creation underwent 3-dimensional (3D) TOF-MR. Imaging was performed at 3 T with a scan acquisition time of approximately 15 min. The technique was similar to head and neck magnetic resonance angiography (MRA), except presaturation bands were not used, thereby allowing simultaneous visualization of both arterial and venous flow. A total of 19 TOF-MR studies were performed.

RESULTS

Nineteen patients underwent imaging and were the focus of this study. Seventeen of 19 TOF-MR studies were of diagnostic quality and yielded findings which enabled the vascular surgeon to take corrective measures. Findings included inflow stenosis, anastomotic narrowing, venous outflow stenosis, and hemodynamically significant venous tributaries. Twelve of 17 patients required conventional digital subtraction angiography (DSA). The congruence rate between TOF-MR and DSA was 83.3%. Four patients (21%) avoided DSA and went directly to definitive surgical treatment including branch ligation (3) or new access (1).

CONCLUSIONS

This is the first report in the literature of successful implementation of 3D TOF-MR to assist in identifying AVF maturation problems. This unique noninvasive imaging modality provides actionable images without contrast or radiation exposure and can obviate the need for invasive diagnostic procedures or provide an anatomic map for planning corrective intervention.