Patient evaluation prior to placement of hemodialysis arteriovenous access

INTRODUCTION — Several characteristics must be present for an arteriovenous (AV) access to be usable for hemodialysis. These include accessibility while the patient is seated; the ability to cannulate the access reliably and repeatedly, which requires a superficial access that is straight for a sufficient length; and adequate blood flow, which relies on unobstructed outflow.

Individualized, patient-centered dialysis access planning is an essential element in the management of the patient with chronic kidney disease (CKD). The goal is to minimize primary failure and to improve the cumulative patency rates with few or no additional interventions. The three choices for hemodialysis vascular access are an AV fistula, an AV graft, or central venous catheter. Although there is general agreement that the best vascular access for the dialysis patient is a functioning AV fistula, an AV fistula may not be possible in all patients and in some patients is not the most appropriate choice.

The decision as to the type of vascular access that is appropriate for an individual patient is a complex one. Among the issues that affect the decision include the patient's medical status (stage of CKD, life expectancy, presence of comorbidities, psychologic concerns, etc), anatomic considerations (availability of suitable vessels, presence of arterial disease), and if they are already on hemodialysis using a tunneled dialysis catheter. (See "Approach to the adult patient needing vascular access for chronic hemodialysis" and "Arteriovenous fistula creation for hemodialysis and its complications" and "Arteriovenous graft creation for hemodialysis and its complications".)

PATIENT EVALUATION — Evaluation of the patient with advanced chronic kidney disease (CKD) in preparation for the placement of a dialysis access is extremely important. Proper patient selection will materially enhance the opportunity to place the proper access type in the proper patient. This evaluation should be detailed and complete [1]. The evaluation of a patient for hemodialysis arteriovenous (AV) access is primarily directed toward the creation of an AV fistula. This evaluation should be composed of several components:

●Medical history

•General medical history

•Assessment of risk factors

●Physical examination

•General physical examination

•Examination to detect pathology that might adversely affect access placement

●Vascular evaluation

Medical history — In obtaining a medical history from the patient, emphasis should be placed upon aspects that might affect the placement of the vascular access as well as determining their overall general medical status. A prior history of the insertion of central venous catheters, peripherally inserted venous or arterial catheters, and the placement of any type of cardiac rhythm device with transvenous leads should be sought. A history of any previous dialysis vascular access placements needs to be elicited. Also, a planned kidney transplant at an early date can affect some of the decisions concerning vascular access that need to be made.

Careful attention should be paid to the detection and evaluation of the severity of risk factors for vascular access placement. The advanced CKD population frequently has multiple comorbidities that can influence decisions related to vascular access (eg, race/ethnicity, sex, cardiac disease, vascular disease, and pulmonary hypertension) [2]. A history of coronary or peripheral artery disease (PAD) can also affect decisions concerning vascular access placement. A history of malignancy, heart failure, or severe coronary artery disease might have implications concerning the patient's life expectancy. (See "Primary failure of the hemodialysis arteriovenous fistula", section on 'Patient risk factors' and "Hemodialysis arteriovenous graft dysfunction and failure", section on 'Etiology' and "Risk factors for hemodialysis arteriovenous fistula failure".)

A history of central venous catheter placement including hemodialysis catheters is also a risk factor for the creation of a brachial artery-associated AV fistula. In one study involving 154 cases in which a brachial-cephalic fistula was created, a previous tunneled hemodialysis catheter was associated with predicted cumulative patency loss of the access ipsilateral and bilateral to the prior catheter site [3].

Physical examination — Both a general physical examination and a focused examination directed toward the vasculature used for access creation are important. In addition to evaluating arterial pulses, obtaining differential blood pressures, and performing an Allen test (see 'Arterial evaluation' below), special emphasis should be placed on physical aspects that might affect the placement of the vascular access; special attention should be given to an evaluation of the risk factors. Issues requiring special attention include the following:

●Any physical evidence (scars) from prior central venous access or hemodialysis catheters should be documented (picture 1). In most but not all instances, the patient will give a positive access history [4]. The presence of other scars indicating prior neck or thoracic surgery or trauma should also be noted and may raise the possibility of anatomic distortions that might affect venous anatomy.

●The patient's chest, breast, and upper arms should be evaluated for the presence of swelling or collateral veins. In patients with normal venous pressure, central venous occlusion may not be associated with swelling; however, the presence of collateral veins should alert the examiner to the problem. (See "Central vein obstruction associated with upper extremity hemodialysis access".)

●The presence of a cardiac rhythm device should be noted. The wires associated with such devices rank high on the list of etiologies of central vein stenosis. It is important to avoid ipsilateral transvenous pacemakers and hemodialysis access. (See "Central vein obstruction associated with upper extremity hemodialysis access".)

Side of access

Handedness — The handedness of the individual should be noted. If possible, creating an AV access in the nondominant arm is preferred. During dialysis, the arm with the access will need to be immobile. Having the dominant arm free during the treatment allows patients to engage in activities involving their hand in a more convenient manner. Nevertheless, using the most optimal vessels for the creation of (ideally) an AV fistula takes precedence. In some centers, vascular evaluation is routinely performed bilaterally. In others, the nondominant arm is evaluated first and, if optimal vessels are present, the dominant arm is not evaluated.

Other considerations — Regardless of handedness, an AV access is better suited contralateral to abnormalities of the proximal extremity arterial circulation. Coronary artery steal syndrome has been reported with AV access ipsilateral to inferior mammary artery to coronary bypass graft. Similarly, the patient with subclavian stenosis may develop symptoms of vertebrobasilar insufficiency.

VASCULAR EVALUATION — Vascular evaluation involves the study of the potential target vessels (arteries, veins) in all patients in preparation for the creation of a vascular access. This evaluation is critically important to the success of an arteriovenous (AV) fistula. In general, these studies involve the upper extremity. The prospect for fistula maturation is an important consideration in the selection of vessels for the creation of the access. A review of all studies (more than 50 patients in each study) that related vessel size and fistula maturation revealed that the influence of vessel diameter on access outcomes was highly variable [3]. Most studies documented a strong association between vascular anatomy and outcome, but some studies have demonstrated a minimal effect.

Two issues are important when evaluating the arteries in preparation for the creation of an AV fistula. The vessel must be capable of delivering blood flow at a rate adequate to support dialysis, and the use of the vessel for the creation of an access must not jeopardize the viability of the digits and hand. Arterial narrowing and calcification are relatively common in patients with advanced chronic kidney disease, especially those that with hypertension or diabetes. The presence of a stenotic or calcified artery may jeopardize the surgeon's attempt to create an AV fistula. In addition, stenotic lesions may predispose the patient to the development of hand ischemia once the AV fistula is created. Problems with the arteries should be identified and managed preemptively.

Venous evaluation comprises a detailed examination to determine not only vein diameters but also condition of the veins, which may be not be optimal due to a variety of factors, most commonly prior injury. Studies demonstrate structural alterations prior to any access surgery [5,6]. Because of these issues, when a vascular problem is detected that will affect the ability to create an AV fistula is detected, it is more likely to be venous than arterial.

Arterial evaluation — The arterial evaluation should include arterial pulse examination, differential blood pressure measurement, and the Allen test [7,8]. In special situations, imaging or other physiologic studies (eg, reactive hyperemia) may be appropriate (figure 1).

Arterial pulses — The axillary, brachial, radial, and ulnar pulses should be examined in both upper extremities to assure that the vessels are patent. A handheld bidirectional Doppler device is very useful for this purpose (picture 2 and picture 3). The quality of these pulses should be scored as either normal (2+), diminished (1+), or absent (0). If a pulse is not palpable, the patient should be referred for a noninvasive vascular imaging, typically duplex ultrasonography. (See 'Arterial diameter' below.)

Differential blood pressures — Differences in blood pressure between the two arms (measured sequentially) should be evaluated. A difference <10 mmHg is normal, a difference of 10 to 20 mmHg is considered marginal, and >20 mmHg is indicative of stenosis and suggests the possibility of subclavian, brachial, or proximal axillary artery stenosis (vessels above the level of the cuff) in the extremity with the lower pressure. The evaluation and treatment of upper extremity arterial disease is discussed separately. (See "Noninvasive diagnosis of upper and lower extremity arterial disease", section on 'Upper extremity segmental pressures' and "Upper extremity atherosclerotic disease".)

If there is a suggestion of subclavian stenosis, there are two options: move to the opposite arm or initiate a more detailed evaluation of the arterial anatomy with the goal of making a definitive diagnosis and treating the problem while considering dialysis access options in that arm. The choice depends upon the circumstances of the individual case. A combination of both may be appropriate in some cases. It should be noted that since the arterial disease that results in a subclavian lesion is generally systemic, the arm with the higher systolic pressure may also be affected as well. Failure to recognize this early presents a risk for the development of hand ischemia following the creation of an ipsilateral dialysis access. (See 'Arterial diameter' below.)

Allen test — The Allen test (or, more accurately stated, the modified Allen test) is used to evaluate the blood supply of the hand. The presence of an optimally functioning dual circulation to the hand, as represented by the radial and ulnar arteries communicating distally through the superficial and deep palmar arches (figure 2), is an important safeguard against hand ischemia. When the radial artery is used for the AV access, a normal and patent ulnar artery can usually support the perfusion of the hand.

We suggest using pulse oximetry as an aid to the Allen test as this makes the test objective increase in effectiveness (figure 3) [9,10]. To perform this evaluation, the pulse oximetry probe should be placed on the patient's index finger. Then, the ulnar and radial arteries should be compressed. The loss of the pulse oximeter waveform is an objective indication that compression is adequate. Subsequent return of a pulse wave following the release of the ulnar artery indicates a negative test (ie, a patent ulnar artery). The test can then be repeated with release of the radial artery to demonstrate its patency [10]. If the radial artery is not patent, then a distal radial artery-based fistula is obviously not possible. If the ulnar artery is dysfunctional, the risk for hand ischemia due to steal is high if the radial artery is used. In these cases, attention should similarly be turned to the opposite arm. When performed with the aid of a pulse oximeter or vascular Doppler, the Allen test has been found to be reliable in 95 to 100 percent of patients being evaluated for future hemodialysis access [11-13].

Reactive hyperemia — Perhaps more important than the diameter of the artery is its functional capacity (ie, its ability to dilate and accommodate the increased blood flow demands of an AV fistula). Reactive hyperemia testing has been advocated as having predictive value for the development of a successful AV fistula [14-16].

The reactive hyperemia test is performed by first obtaining a spectral Doppler waveform of the arterial blood flow and then comparing it with one obtained after the patient has clenched their fist very tightly for two minutes (some have used three minutes). Normally, the Doppler waveform should change from triphasic high-resistance flow to one that is biphasic, indicating low-resistance flow (waveform 1). This effect is mediated by nitric oxide released from the endothelium [17].

One early study reported that a lack of an appropriate reaction after unclenching the fist was significantly associated with increased rates of primary AV fistula failure (figure 4 and table 1) [15]. Later, the same author reported that comparison of the resistive index (RI) before and after the test (as a ratio of RI with reactive hyperemia to RI at rest) improved the predictability of the test, where RI was defined as [14]:

In a group of 116 patients, the rate of successful AV fistula creation was higher for an RI ratio (reactive hyperemia/rest) that was ≤0.70 compared with >0.70 (95 versus 39 percent) [14].

In another report, the hyperemic response was elicited by inflating a blood pressure cuff placed on the upper arm to 20 mmHg above the systolic pressure for three minutes [16]. The response in the artery being evaluated was measured by subtracting the peak systolic velocity (PSV) at rest from the PSV obtained after the period of ischemia. The hyperemic response was recorded for both brachial and radial arteries. They concluded that an AV fistula created using an artery with a hyperemic response that is less than a 5 cm/second increase in PSV was twice as likely to fail as was one created with a response greater than that level. In addition, an AV fistula constructed using a radial artery with a hyperemic response that is less than a 5 cm/second increase in PSV was 4.5 times as likely to fail as was one created using a brachial artery with a response >5 cm/second increase in PSV.

Arterial diameter — The anatomy of the artery that will be used to create the AV access is important to the success of the procedure. The determination of arterial size appropriate for the inflow vessel of a successful AV access is based upon imaging.

A generally recognized standard for arterial diameter does not exist, although a 2 mm minimum threshold has been most frequently quoted (image 1). The KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update advises against using an absolute minimum threshold [1]. However, if a vessel <2 mm is to be used, careful evaluation of its quality and feasibility to produce a functional AV fistula should be evaluated prior to surgery.

Practice guidelines of the Society of Vascular Surgery do not endorse a specific arterial diameter [8]. They simply state that studies have shown more than one size to be the minimally acceptable threshold, but that 2.0 mm appears to be the more commonly accepted limit in adults. Some investigators have suggested using a different minimum arterial diameter threshold [14,15,18-20]. Unfortunately, these diverse reports are all small and have no randomized controls or are underpowered. The disparities in these studies suggest that while artery size is an important consideration, it is not the only determinant for the development of a successful AV fistula. The combination of arterial diameter and venous diameter is an important variable [3]. (See 'Vein size' below.)

Inadequate arteries — With the increasing age of the dialysis population and the frequency of diabetes and hypertension as comorbidities, arterial occlusive disease is commonly encountered in the patient being evaluated for hemodialysis AV access. The presence of peripheral atherosclerotic occlusive disease affecting the proximal arteries is suggested by abnormal blood pressure testing. (See 'Arterial pulses' above.)

Patients with diabetes commonly display medial calcifications of the peripheral arteries in the forearm that can complicate the technical aspects of creating the surgical anastomosis [21,22]. In addition, such lesions can hinder the maturation process by preventing the compensatory hypertrophy of the feeding artery and the subsequent increase in the arterial flow. Unrecognized lesions that are hemodynamically significant can also predispose to hand ischemia. Some have suggested obtaining a preoperative plain radiograph of the hand and forearm as part of the evaluation of the diabetic patient to look for vascular calcification as an aid in the planning of the AV access (image 2) [21].

There are instances in which arteries that are suboptimal for the creation of an AV access are identified in a patient with critical need for the access. There has been only anecdotal experience in prospectively characterizing and treating these cases in an effort to facilitate access creation. In one study, a radial-cephalic AV fistula was created in seven patients in whom radial artery stenosis had been diagnosed by ultrasound evaluation prior to surgery [23]. At the time of surgery, angioplasty was performed on the radial artery. The AV fistula developed adequately to be cannulated at 15 to 90 days postsurgery in six cases.

Venous evaluation — Vascular problems affecting access creation are more likely to be venous than arterial. The veins of the extremity are frequently the object of the iatrogenic injury as a result of venipuncture or central venous access. In addition, some studies show that some structural abnormalities can occur in patients with end-stage kidney disease independent of any arteriovenous (AV) access surgery [5,6].

General characteristics — To ensure the venous outflow of the arteriovenous access meets the desired AV access characteristics, imaging is required to evaluate the entire extent of the vein and its drainage. In addition to evaluating vein diameter and depth (image 3), assessment of the capacity to dilate may also be of value [14,24-26].

Vein distensibility — Several reports have stressed the importance of evaluating vein distensibility (VD) when performing vascular mapping (image 4) [14,24-26]. Several methods have been used, including anatomic and physiologic studies.

The most commonly used approach is to inflate a blood pressure cuff or use a tourniquet above the veins to demonstrate anatomically that the vein is capable of dilating at least 50 percent of the resting internal diameter [14]. Some investigators have gone further and devised methods to more accurately quantify vein dilation.

●In one study, forearm VD was measured using strain-gauge plethysmography in addition to arterial and venous diameters in a small series of patients prior to AV fistula creation [25]. The rate of functional AV fistula among those with a VD >0.50 mL/mmHg was significantly higher compared with those with a VD of ≤0.50 mL/mmHg (80 versus 0 percent). No significant differences were found for arterial or venous diameters for functional versus nonfunctional AV fistulas.

●In another study of 50 cases, procedural success was significantly improved for cephalic veins whose diameters increased more than 0.35 mm after inflating a blood pressure cuff on the upper arm to a level sufficient to stop superficial venous return for one minute [24].

●In a larger observational study involving 122 patients, only vessel diameter and vein distensibility had significant predictive value [26]. The overall cumulative success rate of AV fistula maturation was 89 percent. In this study, the VD threshold separating successful from unsuccessful cases was >0.4 mm, the difference in vein diameter before and after application of a tourniquet for two minutes.

Other physiologic methods are also used to determine the ability of veins to dilate [27]. In the Hemodialysis Fistula Maturation Study, up to five preoperative vascular function tests were administered to each patient [28]. Greater nitroglycerin-mediated or flow-mediated dilation were associated with significantly greater six-week AV fistula blood flow rates and AV fistula diameters.

Vein size — As with arterial size, a generally recognized standard for vein size does not exist. Although some investigators have recommended a different minimally acceptable threshold, the minimum tourniquet-derived venous diameter threshold most often quoted is 2.5 mm at the point of the anastomosis [29]. However, in a study of 202 radial-cephalic and 154 brachial-cephalic AV fistulas, venous diameter >3 mm or >3.4 mm were important for success with a radial-cephalic and brachial-cephalic accesses, respectively [3]. As with the arterial component, the KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update advises against using an absolute minimum threshold [1]. If a vessel <2 mm is to be used, careful evaluation of its quality and feasibility to result in a functional AV fistula should be evaluated prior to surgery.

Most studies addressing vascular anatomy in relationship to success of AV fistula creation have not considered the artery-vein combination in their analysis. In a study involving both radial-cephalic and brachial-cephalic AV fistulas, a combination of radial artery diameter <2.1 mm and vein diameter <3 mm strongly predicted maturation failure (HR 0.24, 95% CI 1.71-10.49) and loss of cumulative patency (HR 4.03, 95% CI 1.88-8.64) for radial-cephalic accesses [3]. While a vein diameter <3.4 mm independently predicted cumulative patency loss (HR 2.12, 95% CI 1.02-4.46), brachial artery diameter was not associated with access maturation or patency; however, arterial diameter was significantly greater than 2 mm in all cases.

Inadequate veins — The standard of practice for the creation of an AV access is to start distally (forearm) in the nondominant arm and to move proximally. If an optimal anatomy is not present in the nondominant arm, then a site on the dominant extremity should be sought. Unfortunately, there are cases in which a suitable vein for the construction of an AV fistula is not present. In these cases, an AV graft should be placed using the same priorities of location. This allows for initiation of dialysis and serves to mature the draining veins, making them suitable for the creation of a secondary AV fistula in the future.

VASCULAR IMAGING — Vascular imaging represents an important aspect of patient evaluation prior to AV access placement and can be accomplished using duplex ultrasound or angiography. Regardless of the imaging technique used, the evaluation of vein diameter should be performed with the aid of a tourniquet to create venous distention. This is thought to more closely approximate the size of the arterialized vein after fistula formation [30].

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) Clinical Practice Guideline for Vascular Access: 2019 Update recommends reserving vascular imaging for potentially problematic cases such as in patients with advanced age, obesity, multiple comorbidities, vascular disease, prior failed dialysis vascular accesses, patients with prior peripherally inserted central catheter (PICC) insertions, multiple central venous catheters, implantable electronic devices, trauma to vascular access target area and drainage, or an inability to perform an adequate physical examination [1]. Unfortunately, a large percentage of patients presenting for evaluation for AV access placement fall into one of these categories. The plan for AV access created based on physical examination alone is frequently altered if imaging is obtained. In a study of 39 cases that were first evaluated by physical examination and then by ultrasonography, the surgical plan for the AV fistula was changed in approximately one-third of the cases [31]. In another study involving the creation of 137 AV fistulas, physical examination, ultrasonography, and venography were performed in all cases [32]. The surgical plan derived from physical examination was changed by the ultrasound results in 23 percent of cases and by 9 percent by venography results.

Two randomized trials formed the basis for the KDOQI physical examination primary opinion. Both studies compared physical examination with ultrasound [33,34].

●The first of these evaluated 186 patients and found that only 80 (43 percent) fulfilled their inclusion requirements for evaluation by physical examination [33]. Of these, 70 patients were randomized. The number of cases achieving a functional fistula (predominantly forearm fistulas) did not differ between the two groups. The rate of intervention per 1000 patient days was lower in the ultrasound group compared with the physical examination group (4.4 + 14.7 versus 19.1 + 65.4), but this difference was not statistically significant.

●In the second trial, the ultrasound group had a significantly lower rate of immediate failure (4 versus 11 percent) [34]. While primary AV fistula survival at one year was similar, assisted primary AV survival at one year was significantly better for the ultrasound group (80 versus 65 percent).

Further supporting imaging is a meta-analysis of five trials comparing physical examination to ultrasound, ultrasound was found to be superior to physical examination [35]. The study authors suggested that routine ultrasound should always be performed to supplement clinical evaluation prior to AV fistula creation.

Duplex ultrasound for vascular mapping — To avoid the risks and complications associated with arteriography, we suggest using ultrasound as a first-line imaging study for arterial evaluation, which is adequate given the high degree of concordance between the duplex and arteriography (image 1) [15,35].

Detailed preoperative vein mapping using ultrasound is the most commonly used method for imaging the venous anatomy prior to access placement [1,2,4,36]. The technique used for ultrasound involves assessing venous anatomy at various separate points along the course of the veins. This makes it impossible to inform the surgeon about the exact course of the vessel and any tortuosity that may be present. Ultrasound has become the become the standard of practice due to its noninvasive nature, ease in measuring depth, and internal diameter of the vessels (image 5), low cost, and applicability in most patients. Other advantages of ultrasound are the ability to perform dynamic studies and that it does not require administration of intravenous radiocontrast media.

The main disadvantage of duplex ultrasound is an inability to directly image the central veins; however, right and left subclavian and internal jugular venous spectral Doppler waveforms can be analyzed for indirect evidence of stenosis or occlusion in the central portion of the subclavian vein, brachiocephalic vein, and superior vena cava. This can be inferred by detecting diminished respiratory phasicity and diminished transmitted cardiac pulsatility in the subclavian and jugular veins (waveform 2) [35,37,38].

To properly evaluate the patient, it is necessary for the examiner to have access to the entire extremity and be able to position it in an optimal manner. If the patient has an open wound, a fresh incision, skin ulceration, a bandage that cannot be removed, or a cast, that area cannot be properly evaluated. In addition, if there is an inability to move the extremity due to contraction or some other permanent or temporary condition, an adequate examination is not possible.

Angiography for venous mapping — Angiographic venous mapping is mainly used in the following situations:

●Ultrasound demonstrated significant abnormalities, which are not completely defined

●High-quality ultrasound is not available

●The institution preference is for bimodal vascular mapping, which combines ultrasound and angiography

Angiography provides excellent visualization of extremity and central venous vasculature (image 6). Since the entire course of the vein can be visualized, angiography provides a more precise assessment of vessel anatomy. This allows the surgeon to assess vessel tortuosity, overall vascular configuration, and to accurately identify abnormalities.

The concern about using angiography for vascular evaluation prior to AV access placement is the exposure of a predialysis patient to the nephrotoxic effects of radiocontrast. These patients, whether already on dialysis or approaching the need for dialysis, often have residual renal function that needs to be preserved. Angiography can generally be accomplished using a relatively small volume of radiocontrast. While there are no randomized trials determining the magnitude of effect in these cases, three observational studies of patients with chronic kidney disease stage 4 and 5 shed some light on the situation [39-41]. The volume of radiocontrast used was less than 15 mL and the incidence of nephrotoxicity was less than 5 percent; all patients returned to their baseline level of renal function within a week of the study.

Ferumoxytol-enhanced imaging — Ferumoxytol is an ultra-small paramagnetic iron oxide embedded in a carbohydrate coating that has been approved by the US Food and Drug Administration as a therapeutic iron supplement. It is cleared from the circulation by reticuloendothelial system macrophages of the liver, spleen, and bone marrow. Because of its iron content, ferumoxytol has been used as a contrast agent for magnetic resonance (MR) imaging ("off label"). Ferumoxytol has a long half-life (15 hours), which allows for imaging of both venous and arterial vasculature without the need for bolus timing, and imaging of the peripheral and central veins and arteries is excellent.

The use of ferumoxytol-enhanced MR for vascular evaluation in planning AV access placement has been reported. In a study involving 59 participants, 51 AV fistulas were created, of which 24 (47 percent) were successful [36]. Fifteen central venous lesions not previously suspected were identified. Ferumoxytol-enhanced MR angiography and duplex ultrasound identified a similar number of peripheral venous sections unsuitable for fistula creation; however, ferumoxytol-enhanced MR identified more unsuitable arterial sections (37 versus 26 percent). The accuracy of imaging for predicting success of AV fistula creation was determined based on the following:

●Ferumoxytol-enhanced MR angiography of central and peripheral vessels

●Ferumoxytol-enhanced MR angiography of peripheral vessels alone.

●Patient age, sex, and ultrasound results

Among the three models studied, ferumoxytol-enhanced angiography of the central and peripheral vessels predicted AV fistula outcome the best. The inter-reader agreement for measurements of the arterial diameter, venous diameter, and vein depth from skin surface was excellent.

Ferumoxytol is safe for MR imaging of patients who had not yet begun dialysis, without the concerns of toxicity associated with iodinated or gadolinium-containing contrast material. However, allergic reactions are possible. Ferumoxytol should not be used in a patient with a history of allergy to any intravenous iron product. Although more expensive compared with ultrasound, ferumoxytol-enhanced MR angiography appears to be useful for patients with borderline vessels by duplex ultrasound or previous failed access, and those with risk factors for central venous stenosis or peripheral arterial disease.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dialysis" and "Society guideline links: Hemodialysis vascular access".)

SUMMARY AND RECOMMENDATIONS

●An arteriovenous (AV) hemodialysis access is a deliberate connection between an artery and vein achieved by anastomosing native vessels or by the interposition of graft material. The goal of AV access creation is to provide an accessible vascular structure with sufficient blood flow that can be cannulated repeatedly to permit adequate dialysis. Several characteristics must be present for an AV access to be usable for hemodialysis. These include accessibility while the patient is seated; the ability to reliably and repeatedly cannulate the access, which requires a superficial access that is straight for a sufficient length; and adequate blood flow, which relies on unobstructed outflow. (See 'Introduction' above.)

●The standard of practice for the creation of an AV fistula is to start distally in the forearm of the nondominant arm and to move proximally. If optimal anatomy is not present in the nondominant arm, then a site on the dominant extremity should be sought. Unfortunately, suitable anatomy may not be present. In these cases, an AV graft should be placed using the same priorities of location. (See 'Inadequate arteries' above and 'Inadequate veins' above.)

●The evaluation includes a medical history, a physical examination, and vascular evaluation. The medical history is directed toward identifying aspects that might affect the placement of the vascular access and risk factors that are associated with AV access failure (eg, central venous stenosis). (See 'Patient evaluation' above.)

●In the planning for vascular access creation, the initial assessment of vascular anatomy should be based upon physical examination. If this fails to disclose an adequate vessel for the creation of an AV fistula, the patient should undergo vascular mapping by ultrasonography. Failure of this modality to identify a usable vein should be followed by further vascular evaluation by venous angiography. (See 'Vascular evaluation' above.)

●Vascular problems affecting AV access creation are more likely to be venous than arterial. To ensure the venous outflow meets the desired characteristics for AV access, the entire extent of the vein and its drainage must be assessed, including vein diameter and depth, and vein distensibility.

●Additional arterial evaluation of importance includes arterial pulse examination, differential blood pressure measurement, and the Allen test. In special situations, imaging and testing of reactive hyperemia may be appropriate. (See 'Arterial evaluation' above.)

●A generally recognized standard for the diameter of the arterial or venous target vessels for AV fistula creation does not exist. Therefore, an absolute minimum diameter threshold should not be used. However, if a vessel <2 mm is to be used, careful evaluation of its quality and feasibility to result in a functional AV fistula should be evaluated prior to surgery using focused vascular evaluations.