You are in: eMedicine Specialties > Radiology > VASCULAR/INTERVENTIONAL Dialysis FistulasArticle Last Updated: Jun 26, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Constantinos T Sofocleous, MD, Assistant Professor, Department of Radiology, University of Medicine and Dentistry of New Jersey Constantinos T Sofocleous is a member of the following medical societies: American College of Radiology, American Heart Association, American Medical Association, American Roentgen Ray Society, and Radiological Society of North America Coauthor(s): Hani H Abu-Judeh, MD, Consulting Staff, Department of Radiology, University of Medicine and Dentistry of New Jersey Hospital; Stanley G Cooper, MD, FACR, FSIR, Interventional Radiologist, Department of Vascular and Interventional Radiology, ProHEALTH Care Associates; Michael Yudd, MD, Medical Director, Dialysis Unit, Department of Veterans Affairs, New Jersey Health Care System; Assistant Professor, Department of Clinical Medicine, New Jersey Medical School; Joaquim Cerveira, MD, Assistant Professor of Surgery, UMDNJ-New Jersey School of Medicine Editors: Gary P Siskin, MD, Associate Professor, Department of Radiology, Albany Medical College; Chief, Division of Vascular and Interventional Radiology, Department of Radiology, Albany Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; George Hartnell, MB, Professor of Radiology, Tufts University School of Medicine, Director of Cardiovascular and Interventional Radiology, Department of Radiology, Baystate Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Kyung J Cho, MD, FACR, William Martel Professor of Radiology, Interventional Radiology Fellowship Director, University of Michigan Health System Author and Editor Disclosure Synonyms and related keywords: arteriovenous dialysis access, arteriovenous fistula, prosthetic polytetrafluoroethylene graft, PTFE graft, chronic renal failure, dialysis, hemodialysis, Dacron, bovine vessels, renal transplantation, percutaneous transluminal angioplasty, PTA, percutaneous thrombolysis, thrombosed graft INTRODUCTIONSection 2 of 10
  The number of dialysis-dependent patients with chronic renal failure is constantly growing. It is estimated that in the Western hemisphere alone, 150-200 cases of chronic renal failure occur per million population annually. The discovery and evolution of hemodialysis techniques have prolonged and improved the quality of life of patients with chronic renal failure. Hemodialysis fistulas are surgically created communications between the native artery and vein in an extremity. Direct communications are called native arteriovenous fistulas (AVFs). Polytetrafluoroethylene (PTFE) and other materials (Dacron, polyurethane, bovine vessels, saphenous veins) are used or have been used as a communication medium between the artery and the vein and are termed prosthetic hemodialysis access arteriovenous grafts (AVGs). The access that is created is routinely used for hemodialysis 2-5 times per week.1 Many patients who are not candidates for renal transplantation or those for whom a compatible donor cannot be secured are dependent on hemodialysis for their lifetime. This situation results in the long-term need for and use of dialysis access. The preservation of patent, well-functioning dialysis fistulas is one of the most difficult clinical problems in the long-term treatment of patients undergoing dialysis. As many as 25% of hospital admissions in the dialysis population have been attributed to vascular access problems, including fistula malfunction and thrombosis. Historically, native fistula or graft malfunction and thrombosis were treated by using surgical thrombectomy and revision, resulting in the eventual exhaustion of the veins and the need to create a new access. Initially applied in the 1980s, percutaneous techniques such as balloon angioplasty (percutaneous transluminal angioplasty [PTA]), thrombolysis, and mechanical thrombectomy allowed the treatment of stenosis and fistula thrombosis without surgery. During the past 15 years, interventional radiologists have increasingly been involved in angiographic evaluation and treatment of malfunctioning and occluded hemodialysis access. The multidisciplinary management of dialysis access coordinated among interventional radiologists, vascular surgeons, and nephrologists has proven extremely effective in prolonging the patency of the vascular access and decreasing the morbidity and mortality of patients with chronic renal failure.2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 EVALUATION AND TREATMENT OF MALFUNCTIONING DIALYSIS ACCESSSection 3 of 10
Less than 15% of dialysis fistulas remain patent and can function without problems during the entire period of a patient's dependence on hemodialysis. The mean problem-free patency period after creation of native fistulas is approximately 3 years, whereas prosthetic PTFE grafts last 1-2 years before indications of failure or thrombosis are noted. After multiple interventions to treat underlying stenosis and thrombosis, the long-term secondary patency rates for native fistulas are reportedly 7 years for fistulas in the forearm and 3-5 years for fistulas in the upper arm; prosthetic grafts remain patent for up to 2 years. To the authors' knowledge, all observations and publications reported to date indicate that for prosthetic grafts, fistula failure and eventual occlusion occur most commonly as a result of the progressive narrowing of the venous anastomosis; for native fistulas, failure occurs most commonly as a result of the narrowing of the outflow vein. In some reports, venous anastomosis is identified in more than 90% of grafts. The primary underlying pathophysiologic mechanism responsible for causing the failure is intimal hyperplasia at the anastomotic site. Additional causes include surgical and iatrogenic trauma, such as repeated venipunctures. Stenoses along the venous outflow and in intragraft locations (for prosthetic PTFE grafts) are also common and require appropriate treatment. Indications for consultation with an interventional radiologist include the following:
The presence of an infection is the only absolute contraindication to angiography and percutaneous treatment of a dysfunctional or thrombosed dialysis access. Angiographic examination of the entire arteriovenous access from the inflow native artery to the right atrium is undertaken to evaluate a failing hemodialysis access. It is important that all underlying lesions be identified and treated. Even in cases in which a stenosis has been identified on sonograms, additional lesions should be searched for and treated to prevent occlusion and recurrence of access malfunction. Angiography is performed under sterile conditions after (1) a direct puncture is made in the arterial limb of the graft with the needle pointing toward the venous outflow or (2) a puncture is made in the native vein of the AVF just distally to the anastomosis. Angiography may be performed by using the outer plastic sheath of a 19-gauge angiocatheter or by using a 4F sheath of a micropuncture set. Arterial anastomosis must always be evaluated. This is achieved by injecting contrast material via the same access site as described above during a temporary occlusion of the outflow with the use of manual compression or a pressure cuff to allow reflux of contrast agent via the anastomosis into the native artery. In addition to venous lesions, the arteriovenous anastomosis and the nearby portion of the native artery also should be evaluated. In patients with native AVFs, a direct arterial puncture may be performed to evaluate inflow problems. In certain instances, evaluation to the level of the subclavian and innominate arteries is performed to identify the underlying stenosis. PERCUTANEOUS TRANSLUMINAL ANGIOPLASTYSection 4 of 10
Percutaneous transluminal angioplasty (PTA) should be performed to treat hemodynamically significant anastomotic and outflow venous lesions and purely arterial inflow stenoses after the fistula is accessed toward the venous and arterial limbs or, in native fistulas, the arteriovenous anastomosis. A hemodynamically significant lesion is usually identified on angiography, because a stenosis causing a decrease in luminal diameter of more than 30% may be accompanied by the formation of collaterals (see Images 1-4). Once identified, most venous lesions can be treated with the use of PTA. The latest results from centers implementing aggressive surveillance programs and PTA treatment in identified stenoses demonstrate a significant decrease in access graft thrombosis and replacement rates. Patency rates can be prolonged by repeating PTA procedures as required without sacrificing the outflow vein. Direct comparisons between PTA and surgical revisions are not easy and are rarely undertaken. The percutaneous approach allows detailed angiographic evaluation of the entire fistula to the right atrium, as well as PTA of identified lesions, during the same session. PTA and stent deployment can be performed in most patients via the initial angiography puncture site of the access and after appropriate dilatation and vascular sheath placement, without surgical incision. A second retrograde puncture (ie, a puncture toward the arteriovenous anastomosis) may be needed to treat stenoses close to the anastomosis of native fistulas. Treatment may be performed in an outpatient setting; the access may be used for hemodialysis immediately after the procedure. STENT DEPLOYMENTSection 5 of 10
Although a variety of stents are available, self-expanding stents are generally preferred for the treatment of dialysis access stenosis because of their flexibility and radial force. Most interventional radiologists agree that a stent is indicated to treat PTA-related flow-limiting ruptures or dissections that persist after prolonged local balloon inflation. Relative indications, such as recoil of a previously successfully treated stenosis by PTA, should be treated after a discussion with the vascular surgeon and after the surgical options and possible future access sites are evaluated. The discrepancy between the reported results after stent deployment in the central veins and the observed stenosis recurrence in the stent or at its edges makes the systematic use of stents in the central vein questionable. The patency of a given vascular access is thus prolonged significantly, although most published reports indicate that this is the result of multiple procedures that are required after stent deployment to maintain good fistula function. Stent placement is contraindicated in patients with PTA-resistant stenoses.15, 16 TREATMENT OF THROMBOSED HEMODIALYSIS ACCESSSection 6 of 10
Thrombosis of dialysis access is an unfortunate but common event in patients with grafts who undergo long-term dialysis. Thrombosis occurs more rarely in native fistulas. Thrombosis is the result of progressive narrowing in 1 of multiple sites in the arteriovenous shunt and its pathway to the right atrium. Historically, temporary hemodialysis catheter placement and/or surgical thrombectomy with hospital admission were the only available treatments. Typically, with surgical treatment, a portion of the outflow vein is sacrificed. Repeated surgical revisions soon exhaust the available sites for peripheral access, exasperating patients and physicians alike. Currently, in a growing number of institutions, percutaneous treatment is available on an outpatient basis, generally within 24 hours of the event. The consequences of thrombosis of hemodialysis access with regard to patients' quality of life, to public health concerns, and to society in general are well known. The advantages of percutaneous radiologic interventions for the surveillance and treatment of the failing access also apply to clotted grafts and fistulas. Angiography is performed to evaluate the condition of the outflow to the right atrium (and, for native fistulas, inflow) before any attempt is made to recanalize an occluded access. The entire recanalization procedure is completed within hours, after which the patient can be discharged and the access used immediately for dialysis. Perhaps the most valuable benefit of percutaneous declotting is the preservation of the entire outflow vein. Repeated procedures can be performed to preserve access patency. Percutaneous thrombolysis Many percutaneous techniques with comparable results have been described in the treatment of hemodialysis access occlusion. One of the first and most commonly performed techniques is pulsed-spray thrombolysis (PST) with urokinase (UK) and PTA. The technique underwent several modifications, which mostly shortened the initial procedure time to less than 2 hours and decreased the overall amount of thrombolytic agent needed. Since the disappearance of UK from the US market in 1999, different forms of tissue plasminogen activator (t-PA) have been used in PST, with similar results.17, 18, 19, 20, 21, 22, 23, 24, 25 Additional recanalization techniques include balloon thrombectomy and thromboaspiration, PST with sodium chloride solution and heparin, and the use of a series of mechanical thrombectomy devices.26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 Procedure The graft is accessed in a crisscross manner.
RESULTS AND COMPLICATIONSSection 7 of 10
Results Most series define success as complete recanalization of the thrombosed graft such as to allow at least 1 successful dialysis session within 24 hours of the procedure. Success rates reported in the literature have been similar, ranging from 71% to 100%. Long-term results of graft recanalization are usually evaluated by calculating primary and secondary patency rates from Kaplan-Meier life tables.
It is noteworthy that success rates are similar for prosthetic PTFE grafts and forearm native fistulas, though most interventional radiologists agree that declotting a native fistula is technically more challenging than declotting a graft. In addition, the results clearly appear to be more durable after recanalization of a forearm native fistula, though repeat intervention is much more common for prosthetic grafts and upper-arm fistulas. Complications Overall complication rates are low — typically, 0-16%. Complications include arterial emboli (1-7%), post-PTA flow-compromising ruptures (2-5%; the rate can be higher in native fistulas of upper arm [15%]); fluid overload or pulmonary edema; reactions to the contrast agent; extravasation hematomas at puncture sites of previous dialysis procedures; infection; and death (very rare). Death may result from cardiac arrhythmia, pulmonary edema, or a reaction to the contrast medium. Although clots may migrate into pulmonary circulation, clinically evident pulmonary embolism has been reported in only 6 cases; however, pulmonary embolism may occur with native fistulas. Although pulmonary embolism has been reported, it is extremely rare during thrombolysis of hemodialysis access grafts. Most complications are treated by the interventional radiologist during the procedure. Arterial emboli are retrieved with an embolectomy or with the use of a Fogarty balloon thromboaspiration, or they are treated with local infusion of a thrombolytic agent (UK or t-PA). Although there is a theoretical risk of serious complications during thrombolysis with any of the thrombolytic agents (UK, streptokinase, t-PA), life-threatening bleeding complications are extremely rare. Post-PTA ruptures have been treated successfully with prolonged balloon inflation and the deployment of uncovered and, more recently, covered stents, as needed. If needed, stent deployment may be used to keep the pathway toward the right atrium patent. These options usually allow completion of the procedure and salvage of the arteriovenous graft or native fistula. Fluid overload and pulmonary edema can be avoided by providing hemodialysis via a temporary catheter in all patients who do not undergo dialysis for more than 72 hours before the recanalization procedure. When fluid overload occurs during or after the procedure, it can be treated medically with appropriate methods, including oxygen therapy and the administration of diuretics.46 CONCLUSIONSection 8 of 10
Technological progress in the field of interventional radiology and device manufacturing has allowed a large number of procedures to be performed without open surgery. One of the fields in which this approach has flourished is the treatment of failing and thrombosed dialysis access. Direct comparison with the surgical treatment of graft thrombosis is not easy, and when patency rates are involved, the comparison is meaningless, because the surgical literature determines patency from the time of graft placement or fistula creation, whereas assessment of nonsurgical interventional procedures begins from the point of failure or thrombosis. Very few small, randomized trials have been conducted comparing the results and failures of nonsurgical interventions and surgical procedures. With the exception of certain stent locations, most nonsurgical interventional procedures do not prohibit future surgical revision if and when needed. Nonsurgical procedures can also be used to recanalize the access site without sacrificing any fragment of the venous outflow, thereby prolonging the use and overall life of the access. Several percutaneous techniques have been studied, with comparable results. In the literature, sufficient evidence has proven that nonsurgical interventional treatment of hemodialysis access failure and thrombosis provides good and durable results when performed by experienced operators. This assessment is supported by the latest US National Kidney Foundation's Kidney Disease Outcomes Quality Initiative guidelines for graft maintenance. With the advent of new devices and the continuous improvement of existing devices, the percutaneous treatment of failing and occluded dialysis access will continue to improve in the future. The role of the interventional radiologist is changing. The radiologist's role has changed from that of an angiographer who makes the diagnosis into that of a physician who treats patients with chronic renal failure in coordination with the nephrologist and the vascular surgeon. MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
Article Last Updated: Jun 26, 2008 | ||||||||||||||||||||||||||||
