Management of vascular access inflow-outflow imbalance: A bimodal approach.

A more accurate descriptive and clinically useful diagnosis based upon pathophysiology for what is commonly referred to as venous outflow stenosis is inflow-outflow imbalance. In these cases, the total outflow capacity of the AV access is inadequate to handle the inflow volume (Qa) without an increase in pressure. The relative inadequacy of the access outflow capacity in comparison to Qa results in increased outflow resistance and a proportional increase in intraluminal pressure. The clinical indicators associated with venous stenosis are the resulting manifestations of this imbalance. The point at which this occurs is dependent upon variations in these two parameters-Qa and outflow resistance. The variations in these two parameters are considerable and reciprocal. Excessive Qa results in or can lead to an entire list of serious problems that adversely affect patient morbidity and mortality. Most studies dealing with AV access Qa reduction have been for the treatment of an existing condition rather than its prevention; however, prevention of disease rather than waiting for its development is an important tenet of medical practice. The resulting clinical picture of inflow-outflow imbalance is taken as an indication for corrective treatment. In the past, in most cases this has meant angioplasty to open the outflow if it is reduced; however, this clinical picture may be associated with an excessive Qa and angioplasty in these cases creates the risk for a further increase in Qa. It is the authors' opinion that access flow measurements should be a part of the evaluation of these cases prior to planning treatment. Using this information, a bimodal approach to primary treatment should be adopted involving either angioplasty for cases with a low or normal Qa or flow reduction in cases with an elevated Qa.

ASDIN white paper: Management of cephalic arch stenosis endorsed by the American Society of Diagnostic and Interventional Nephrology.

Brachiocephalic arteriovenous fistulas (AVF) makeup approximately one third of prevalent dialysis vascular accesses. The most common cause of malfunction with this access is cephalic arch stenosis (CAS). The accepted requirement for treatment of a venous stenosis lesion is ⩾50% stenosis associated with hemodynamically abnormalities. However, the correlation between percentage stenosis and a clinically significant decrease in access blood flow (Qa) is low. The critical parameter is the absolute minimal luminal diameter (MLD) of the lesion. This is the parameter that exerts the key restrictive effect on Qa and results in hemodynamic and functional implications for the access. CAS is the result of low wall shear stress (WSS) resulting from the effects of increased blood flow and the unique anatomical configuration of the CAS. Decrease in WSS has a linear relationship to increased blood flow velocity and neointimal hyperplasia exhibits an inverse relationship with WSS. The result is a stenotic lesion. The presence of downstream venous stenosis causes an inflow-outflow mismatch resulting in increased pressure within the access. Qa in this situation may be decreased, increased, or within a normal range. Over time, the increased intraluminal pressure can result in marked aneurysmal changes within the AVF, difficulties with cannulation and the dialysis treatment, and ultimately, increasing risk of access thrombosis. Complete characterization of the lesion both hemodynamically and anatomically should be the first step in developing a strategy for management. This requires both access flow measurement and angiographic imaging. Patients with CAS present a relatively broad spectrum as relates to both of these parameters. These data should be used to determine whether primary treatment of CAS should be directed toward the anatomical lesion (small MLD and low Qa) or the pathophysiology (large MLD and high Qa).

Catheter-directed thrombolytic infusion for thrombosed arteriovenous fistulas with a large clot burden: A case series.

Arteriovenous fistula (AVF) thrombosis occurs less often when compared to arteriovenous grafts. Since the number of AVFs has increased in the United States, AVF thrombosis is seen more frequently today. AVF thrombectomy can be tedious, requires physician ingenuity, and many times results in failure. Substantial clot burden in megafistulas and aneurysms is considered a relative contraindication to endovascular thrombectomy. Usually, it results in surgical referral for open thrombectomy or, at times, abandonment of the fistula altogether. Herein, we describe the technique, results, and cautions of combining a continuous infusion of recombinant tissue plasminogen (rTPA) followed by angioplasty of the culprit stenotic lesion that was successful in opening five of six AVFs with a substantial clot burden.

Peritoneal Dialysis Catheter Placement: Percutaneous and Peritoneoscopic Techniques.

Chronic peritoneal dialysis (PD) is an underutilized renal replacement therapy in treating end-stage renal disease that has several advantages over hemodialysis. The success of continuous ambulatory PD is largely dependent on a functional long-term access to the peritoneal cavity. Several methods have been developed to place the PD catheter using both surgical and percutaneous techniques. The purpose of this article is to describe the percutaneous techniques using fluoroscopy guidance and peritoneoscope method. While fluoroscopic method uses fluoroscopy guidance and a guidewire to place the PD catheter, the peritoneoscopic technique utilizes a needlescope to directly visualize the peritoneal space to avoid adhesions and omentum during catheter placement. These percutaneous approaches are minimally invasive procedures that can be performed on an outpatient basis without the need for general anesthesia.

To ligate or not to ligate hemodialysis arteriovenous fistulas in kidney transplant patients.

There is significant disagreement about maintenance or ligation of arteriovenous fistulas (AVFs) in kidney transplant patients (KTPs). Potential harms from maintaining AVFs are their impact on cardiac function, cosmetic concerns and complications such as bleeding and rupture. High flow AVFs can place a strain on the heart and cause or exacerbate pre-existing cardiac dysfunction. There is an improvement in cardiac function after kidney transplantation independent of vascular access status. Studies comparing cardiac parameters in patients with and without AVFs after renal transplantation have shown conflicting results. Ligation of high flow AVFs in KTPs resulted in improvement in cardiac function and prevention of heart failure. In KTPs with deteriorating renal function and high flow AVFs, banding of the AVFs to reduce flow is an option. Patients who retain AVFs after renal transplant have the advantage of immediate, optimal access should the transplant fail and may have preserved kidney function. The patient's post-transplant kidney function, risk factors for transplant loss, AVF blood flow, and cardiac function play an important role when making the decision to ligate or preserve AVFs.

Uncommon complications of long-term hemodialysis catheters: adhesion, migration, and perforation by the catheter tip.

Use of long-term dialysis catheters (e.g., tunneled dialysis catheters) predisposes patients to complications. While catheter-related bacteremia is one of the commonest encountered complication, there are a series of rare complications, namely catheter adherence to the vessel wall, catheter fracture, and vessel perforation, that can occur. This article attempts to discuss such complications with emphasis on potential risk factors, clinical presentations, and management options.

Patency rates for angioplasty in the treatment of pacemaker-induced central venous stenosis in hemodialysis patients: results of a multi-center study.

While hemodialysis access ligation has been used to manage pacemaker (PM) and implantable cardioverter-defibrillator (ICD) lead-induced central venous stenosis (CVS), percutaneous transluminal balloon angioplasty (PTA) has also been employed to manage this complication. The advantages of PTA include minimal invasiveness and preservation of arteriovenous access for hemodialysis therapy. In this multi-center study we report the patency rates for PTA to manage lead-induced CVS. Consecutive PM/ICD chronic hemodialysis patients with an arteriovenous access referred for signs and symptoms of CVS due to lead-induced CVS were included in this analysis. PTA was performed using the standard technique. Technical and clinical success was examined. Technical success was defined as the ability to successfully perform the procedure. Clinical success was defined as the ability to achieve amelioration of the signs and symptoms of CVS. Both primary and secondary patency rates were also analyzed. Twenty-eight consecutive patients underwent PTA procedure. Technical success was 95%. Postprocedure clinical success was achieved in 100% of the cases where the procedure was successful. The primary patency rates were 18% and 9% at 6 and 12 months, respectively. The secondary patency rates were 95%, 86%, and 73% at 6, 12, and 24 months, respectively. On average, 2.1 procedures/year were required to maintain secondary patency. There were no procedure-related complications. This study finds PTA to be a viable option in the management of PM/ICD lead-induced CVS. Additional studies with appropriate design and sample size are required to conclusively establish the role of PTA in the management of this problem.

Angioplasty to promote arteriovenous fistula maturation and maintenance.

The arteriovenous fistula is currently the best permanent access for the hemodialysis patient. Unfortunately, stenosis impairs maturation, long-term survival, and function of the arteriovenous fistula. Angioplasty currently is the best procedure for the treatment of immature and dysfunctional arteriovenous fistulas. In this review, the authors discuss the optimum time to evaluate arteriovenous fistulas for maturity, methods of evaluation for maturity, and the role of angioplasty in salvaging immature arteriovenous fistulas. The review also discusses the effect of stenosis on dysfunction in mature arteriovenous fistulas and the role of angioplasty to treat this complication. Finally, the impact of cutting balloons and drug-eluting balloons in the treatment of resistant and recurrent stenosis, respectively, is also discussed.

Thigh grafts contribute significantly to patients' time on dialysis.

BACKGROUND AND OBJECTIVES: Thigh grafts are placed in hemodialysis patients who have exhausted all arm access sites. The goal of this study was to compare the survival, complication rates, and overall contribution of thigh grafts with arm grafts and fistulas in patients with at least one functional thigh graft during their dialysis history. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This longitudinal review of a prospectively acquired clinical database included 85 thigh graft recipients. The rates of survival, thrombosis, infection, and other complications were determined for a total of 268 fistulas, arm grafts, and thigh grafts placed in these patients. RESULTS: In this patient subset, thigh graft primary failure rate was lower than arm grafts and fistulas (3 versus 13 and 61%, respectively). Excluding primary failures, thigh grafts survived longer than both arm grafts and mature fistulas (53 versus 14 and 32%, at 3 years; 47 versus 3 and 11% at 5 years). Thigh grafts had a lower thrombosis rate than arm grafts (0.543 versus 1.457/patient-year) but similar rates of loss as a result of infection and surgical revision. In patients with previous arm accesses, thigh grafts contributed 51% of total dialysis time compared with 38 and 11% for arm grafts and fistulas. CONCLUSIONS: Thigh grafts provide long-term, thrombosis- and infection-free dialysis access for patients with exhausted arm access sites. The decision for thigh graft placement should, therefore, be made as soon as there is evidence for unavailability of arm access sites so that catheter use can be minimized.

The history of interventional nephrology.

Visionary nephrologists in the early 1960s invented the dialysis machine, constructed arteriovenous shunts and fistulas, and designed vascular and peritoneal catheters to provide their patients with long-term dialysis. As the number of dialysis patients grew, the construction and care of vascular access was abandoned by nephrologists to surgeons and radiologists. There was a decline in the number of fistulas and an increase in grafts in the United States. Vascular access was not the first priority for the nonnephrologists, and this set the stage for the emergence of diagnostic and interventional nephrologists. These self-taught nephrologists trained others, resulting in a critical mass of subspecialists who founded the Society of Diagnostic and Interventional Nephrology. This review traces the origin of this exciting field from its pioneers to the society as it exists today. The future of this society depends on academic nephrology fellowship programs fostering training and research in this field.