Physical examination of the mature hemodialysis arteriovenous fistula

INTRODUCTION — Physical examination of the hemodialysis arteriovenous (AV) access is easy and inexpensive and can often detect common problems associated with hemodialysis AV fistula [1-5].

The physical examination of the mature AV fistula is reviewed. Examination of the newly created AV fistula is discussed separately. (See "Early evaluation of the newly created hemodialysis arteriovenous fistula".).

The physical examination of the AV graft is reviewed separately. (See "Physical examination of the arteriovenous graft".)

ACCURACY OF PHYSICAL EXAMINATION — Physical examination of the hemodialysis vascular access is very effective for the prospective diagnosis of complications affecting the AV access, and for planning the approach for endovascular procedures used for the treatment of these complications [1]. Delayed diagnosis of dysfunction often leads to inadequate hemodialysis, complications that can affect the viability of the AV fistula, and prolongation of catheter usage while waiting for access maturation.

The accuracy of physical examination depends upon the experience of the clinician [6,7]. The necessary clinical skills can be taught and improve with experience [6]. In a review of the pertinent literature [8], AV fistula physical examination was shown to have a 75 percent sensitivity and a 76 percent positive predictive value. Some individual studies have shown results superior to these. In one study, the sensitivity, specificity, positive predictive value, and negative predictive value for physical examination in AV fistulas was 96, 76, 86, 93, and 60 percent, respectively [9]. When a physical examination positive for stenosis was combined with access surveillance modalities, either decreased access blood flow or elevated static venous pressure, the sensitivity was 98 percent [8].

Further diagnostic testing — Patients should be referred for diagnostic testing as soon as an abnormality is detected by physical examination. Stenosis, whether related to outflow or inflow, will lead to fistula dysfunction, which results in inadequate dialysis and eventually thrombosis with the risk of loss of the fistula. Options for diagnostic testing include ultrasound imaging or angiography. We prefer angiography because detected abnormalities on physical examination can often be adequately treated by endovascular means with a high expectation of success [10]. (See "Endovascular intervention for the treatment of stenosis in the arteriovenous access".).

ROUTINE EXAMINATION — The hemodialysis AV access is the lifeline for patients with end-stage kidney disease. Unfortunately, it is prone to the development of a range of mechanical problems and other complications (eg, infection). Early recognition of these is important to preserve the patient's ability to receive hemodialysis therapy.

The three basic tenets of physical examination are inspection, palpation, and auscultation, or put more simply, "look, feel, and listen." Some of the problems that affect an AV fistula are easily detected by simple observation, including complications such as aneurysms, pseudoaneurysms, infection, and hemodialysis access-induced distal ischemia (HAIDI).

The nemesis of the hemodialysis AV access is venous outflow obstruction, commonly referred to as venous stenosis. Prospective diagnosis of venous stenosis is an extremely important goal to decrease the risk of AV access thrombosis and its possible loss. This requires a detailed examination. The high accuracy of physical examination alone or in combination with either access blood flow (Qa) or static venous pressure in attaining this goal suggests that physical examination of the AV access should be part of every teaching program for caregivers involved in hemodialysis [8].

Inspection — Inspection should begin with a careful examination of the AV fistula, first identifying the type of access and then inspecting the extremity and the chest wall, comparing the side of the AV access with the contralateral side. AV fistulas should be examined without inserted hemodialysis needles.

Identify type of fistula — Identification of the anatomy of the access is important. Problems that can affect an AV fistula are somewhat different from those that are seen in association with an AV graft. While venous outflow stenosis can occur anywhere within the draining veins, each type of AV access has a specific lesion that represents the most common associated stenosis, which makes identification of the type of AV access important. (See 'Specific lesion characteristics' below.).

In most cases, the difference between an AV fistula and an AV graft is obvious based upon location, associated scars, and configuration. An AV fistula on the anterior surface of the forearm is most likely to be a radial-cephalic AV fistula. An AV fistula on the anterior surface of the upper arm is most likely to be a brachial-cephalic or a brachial-basilic AV fistula. These two can be distinguished by the presence of a scar on the medial aspect of the upper arm. If this is observed, it indicates a brachial-basilic access that has been transposed. An AV fistula present on the medial aspect of the upper arm is a brachial-basilic fistula that has not been transposed. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Types by anatomic location' and "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Vein transposition fistula' and "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Vein translocation fistula'.)

Extremity and chest — Swelling of the AV access arm indicates a global increase in venous pressure within the extremity. This occurs with thoracic central venous stenosis. The thoracic central veins represent the only conduit for outflow. This is contrasted with a peripheral stenosis, for which there are alternative pathways. (See 'Central vein stenosis' below.)

Inspection of the AV access and extremity should also include evaluation for the presence of aneurysms or pseudoaneurysms, the presence of infection, and evidence suggesting ischemia of the hand. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Complications of AV fistula placement'.),

Arm elevation test — The arm elevation test should be included during the inspection of the AV fistula. In the patient with an AV fistula, the access is generally distended when the arm is dependent due to the effects of gravity. When the arm is then elevated to a level above that of the heart, the AV fistula should collapse. This can be taken as evidence that a significant venous outflow lesion is not likely, although an extremely high blood flow can occasionally give a false positive [11,12]. Even a large, dilated AV fistula (ie, megafistula) should become flaccid with arm elevation. However, if a venous stenosis is present, only that portion of the AV fistula proximal (below) to the lesion will collapse with the arm elevated, while that distal (above) to the lesion will remain distended. The arm elevation test along with the pulse augmentation test make up the "10-second AV fistula examination." (See 'Pulse augmentation test' below.)

Palpation — The next step in the physical examination of an AV fistula is palpation. The AV access should be systematically palpated from its origin at the arterial anastomosis through the draining veins up to the subclavian area on the ipsilateral side. In doing this, the character of the pulse and the quality of the thrill are evaluated. These two parameters have significant value in identifying the cause and site of AV fistula dysfunction [12]. In addition, pulse augmentation should be evaluated.

As a rule of thumb, having pulse is bad, indicating downstream stenosis, and having a thrill is good, indicating good access blood flow.

Pulse — Normally, an AV fistula is easily compressible with little, if any, palpable pulse (figure 1). The pulse may be best appreciated using the fingertips.

●In general, a pulsatile AV access is an adverse finding indicative of a downstream (ie, in the direction of flow) stenotic lesion. The degree of hyperpulsatility is proportional to the severity of the stenosis. It should be noted that hyperpulsatility associated with an aneurysm or pseudoaneurysm cannot be used to judge the presence of outflow stenosis. Because of the Bernoulli principle, they will always be hyperpulsatility.

●An unusually weak pulse (hypopulsatile access) or "flat access" suggests the presence of a stenotic lesion located in the inflow side of the access.

Thrill — A thrill is a palpable vibration (ie, "buzz"). It is related to flow, and when present, indicates that there is blood flow within the access. The thrill may be best evaluated by using the palm of the hand (figure 2). The absence of a thrill indicates a lack of flow, which along with the absence of any pulse is characteristic of a thrombosed access.

The normal thrill is a diffuse, background, continuous, machinery-like sensation with a diastolic and systolic component. A normal thrill is palpable over the course of the AV fistula but most obvious at the arterial anastomosis.

A stenotic lesion creates a localized area of turbulent flow within the vessel. As the lesion develops with progressively increasing resistance to flow, the thrill becomes intense, and the diastolic component becomes shortened. Eventually, the diastolic component is lost. The abnormal thrill is most prominent at the site of the stenosis, which helps to localize the lesion. The entire course of the AV fistula drainage should be examined for the presence of an abnormal thrill. With subclavian or cephalic arch stenosis, a thrill can often be detected below the clavicle at the infraclavicular fossa.

Pulse augmentation test — The pulse augmentation test is used to evaluate the quality of the arterial inflow [12]. The test is performed by first assessing the intensity of the pulse in the AV fistula in its normal state. Then the access is occluded using the finger of one hand several centimeters above the anastomosis (figure 3). Once occluded, the increase in the force of the pulse (augmentation) is assessed using the other hand. The degree of increase in pulse intensity is directly proportional to the quality of the access inflow.

The test is also useful when hyperpulsatility due to a downstream stenosis has been noted. If a hyperpulsatile AV fistula does not demonstrate augmentation with occlusion, it suggests that the stenosis is severe, equivalent to complete obstruction. The detection of some degree of augmentation in a hyperpulsatile AV fistula suggests a lesion of lesser severity.

For ease of communication and documentation, it may be useful to grade the degree of pulse augmentation on a scale of 0 to 3. A value of 0 indicates an absence of inflow (ie, the access is thrombosed). Values less than 3 suggest varying degrees of abnormality. This maneuver is sensitive to the detection of problems associated with an AV fistula. In combination, the pulse augmentation test and the arm elevation tests described above have been referred to as the "10-second AV access examination." By using these two tests, the inflow and outflow, respectively, can be quickly assessed. (See 'Arm elevation test' above.)

Auscultation — The next step in the physical examination of the AV access is auscultation. This can be performed using a stethoscope or with a handheld continuous wave Doppler. One advantage of using Doppler is the ability to hear very low flow that distinguishes between a fistula that has a severe stenosis versus one that is completely occluded.

Bruit — The bruit is the auditory manifestation of a thrill and has the same basic implications. The bruit is characterized by both its auditory frequency (pitch) and the duration (figure 4). The bruit over a well-functioning fistula has a low-pitched, soft, machinery-like rumbling sound and, like the thrill, has both a systolic and diastolic component. The bruit is also more accentuated at the arterial anastomosis.

Increasing resistance from a progressively stenotic lesion will result in the progressive loss of the diastolic component of the pulse wave so that the bruit becomes systolic only. With this change, the intensity increases, and the pitch frequently becomes progressively higher, often developing a whistle-like component. The intensity of the bruit is maximal at the point of stenosis. This helps with localization of the lesion. The entire course of the access drainage, including the infraclavicular area, should be examined for the presence of an abnormal bruit.

DETECTION OF SPECIFIC PROBLEMS

Specific lesion characteristics — In addition to those lesions that are obvious upon inspection of the AV fistula, there are a number of specific lesions and pathologies that can be identified and localized using the basic principles as outlined. It should be noted that in general, these descriptions relate to lesions that are sharply defined (ie, not associated with another lesion). All of these conditions represent a spectrum ranging from mild to severe. Conditions that are less advanced will demonstrate abnormalities to a lesser degree. Specific lesions are discussed in more detail below.

Inflow stenosis — Inflow stenosis may be diagnosed by physical examination using the pulse augmentation test. This detects decreased blood inflow, which includes lesions affecting the arterial anastomosis, the feeding artery above the anastomosis, the juxta-anastomotic zone of the access, and those that represent a combination of these sites. Unfortunately, it does not distinguish between them; distinction requires ultrasound evaluation or angiography. However, there are other physical findings that are associated with the juxta-anastomotic lesion that allows it to be detected. (See 'Juxta-anastomotic stenosis' below.)

Outflow stenosis — The differences between the physical examination of a normal AV access and one with outflow venous stenosis are easily recognized.

●Pulse

•Normal – soft, easily compressible

•Abnormal – increased intensity, forceful

●Thrill

•Normal – diffuse, soft, both systolic and diastolic components

•Abnormal – localized to site, accentuated, diastolic component is shortened and may be absent

●Bruit

•Normal – diffuse, low-pitched, both systolic and diastolic components, machinery-like

•Abnormal – localized to site, accentuated, may be high-pitched, diastolic component is shortened and may be absent

Venous outflow stenosis is diagnosed by applying the parameters described above: pulse, thrill, and bruit. The degree of abnormality that is present depends on the severity of the lesion. With increasing severity, resistance to blood flow increases, causing the pulse to become more intense and the diastolic component of the pulse wave to shorten progressively. With a focal decrease in luminal diameter, velocity of flow increases, and turbulence is created. The endpoint is hyperpulsatility of the access with a thrill and bruit that are only in systole. With this change, the bruit becomes more highly pitched and at times has a whistling sound that is heard only during systole. The stenotic site is characterized by turbulent blood flow, which causes the changes in thrill and bruit to be more intense at that point. The AV fistula or vein upstream from the lesion will become progressively more distended, eventually taking on an aneurysmal appearance.

As stated above, there are characteristic lesions that are typically associated with each of the three major types of AV fistula. Although other lesions frequently occur with each major type of AV fistula, the frequency of the characteristic lesion seen in association with each should prompt a high level of suspicion when evaluating a case in which venous outflow stenosis is obvious.

Juxta-anastomotic stenosis — Juxta-anastomotic stenosis is the most common lesion associated with a radial-cephalic AV fistula [13]. This is defined as stenosis that occurs within that portion of the AV fistula that is immediately adjacent to the arterial anastomosis. It seldom extends for more than 3 to 4 centimeters. Although juxta-anastomotic stenosis is a venous lesion, its effect is to adversely affect blood inflow into the AV fistula. Therefore, it will result in decreased pulse augmentation. As stated above, problems with access inflow may represent a combination of lesions.

Three variations of juxta-anastomotic stenosis may be seen: juxta-anastomotic zone only, the juxta-anastomotic zone plus the anastomosis, and both of these plus the adjacent artery. The distinction between the three generally requires angiography for confirmation. The juxta-anastomotic zone-only stenosis is the most common. This lesion can be easily diagnosed by palpation of the anastomosis and distal vein. The vein at the anastomosis is slightly aneurysmal, and a very forceful pulse will be felt at the anastomosis due to the stenosis that is immediately adjacent. The thrill is present only in systole, as is typical for outflow stenosis. In some instances (severe lesion), it may be very short and even difficult to detect. As one moves up the vein from the anastomosis with the palpating finger, the pulse goes away rather abruptly as the site of stenosis is encountered (figure 5). Above this level, the pulse is very weak and may be difficult to detect. The onset of the stenosis itself can frequently be felt as an abrupt diminution in the size of the vein, almost like a shelf [12].

Cephalic arch stenosis — The most common lesion associated with a brachial-cephalic AV fistula is cephalic arch stenosis [13]. The first step in recognition of this lesion is to identify that the patient has a brachial-cephalic AV fistula. The brachial-cephalic and brachial-basilic AV fistulas are located on the anterior surface of the upper arm (figure 6). The two can be distinguished very easily by recognition of the medially placed scar that represents the surgical incision made when the brachial-basilic access was transposed. The absence of a scar identifies this AV fistula. (See 'Identify type of fistula' above.)

Physical examination reveals failure of the access to collapse when the arm is elevated, indicating outflow stenosis. The access is hyperpulsatile. The thrill and bruit felt over the anastomosis are accentuated with a shortening of the diastolic component, which may be totally absent. As one examines the course of the AV fistula, a localized thrill and bruit can be detected at the infraclavicular fossa. This finding may also be seen in association with subclavian stenosis. Lesser degrees of stenosis will give identical findings; however, with central vein stenosis, swelling of the ipsilateral extremity is usually present if the stenosis is severe [12,14].

Brachial-basilic angle of transposition stenosis — The most common lesion associated with a brachial-basilic AV fistula is stenosis at the angle of transposition also known as the "swing segment" (ie, the angle created when the surgeon transposes the medially located basilic vein to an anterior position of the upper arm) [13]. Recognition of this AV fistula is assured by observing a linear scar on the medial aspect of the patient's arm, a sign that the vein has been transposed. The physical findings of this lesion are essentially the same as described above for cephalic arch stenosis, except that the point of abnormal thrill and bruit are associated with the lesion itself. In this instance, following the vein centrally along its course, the point at which it returns to the normal anatomical position is the angle of transposition. With this lesion, a localized thrill and bruit can be detected at that site [12]. The intensity of this finding is proportional to the severity of the lesion.

Thrombosed AV fistula — A thrombosed AV fistula is characterized by a lack of a thrill or bruit. Both physical findings are more obvious at the arterial anastomosis. However, because AV fistulas tolerate much lower blood flow rates without clotting, the stenotic lesion can become more severe before it is detected than is typically seen with an AV graft [15]. Flow can be so diminished that it is no longer detectable, or all the flow (diminished) is going through collaterals. An AV fistula can have collateral flow even after a segment of the fistula has become completely obstructed. From a clinical perspective, when an AV fistula no longer has detectable flow in the dialysis facility, it is generally labeled as a thrombosed AV fistula. However, many of these contain very little or no thrombus. They have a severe degree of stenosis with very little blood flow through the fistula often with a proliferation of collateral vessels. Frequently this results in complex anatomy.

Central vein stenosis — The hallmark of central vein stenosis is swelling of the ipsilateral extremity, the severity of which is proportional to the degree of narrowing of the luminal diameter at the point of lesion. This physical funding is unique to central vein stenosis and would have already been obvious by inspection of the patient's arm. The most common presentation is isolated edema of the ipsilateral arm. However, a severe lesion in the ipsilateral brachiocephalic vein can result in extremity and facial edema, and a lesion in the superior vena cava can cause swelling of both extremities as well as the face. (See "Clinical features, diagnosis, and classification of thoracic central venous obstruction", section on 'Edema and pain' and "Clinical features, diagnosis, and classification of thoracic central venous obstruction", section on 'Collateral venous patterning'.)

With any presentation, hyperpulsatility of the access may not be obvious. This is because of the edema surrounding the access, making it less obvious, and the fact that being a compliant vessel, the distance from the lesion allows for a dissipation of the effect. Often, especially in thin-chested individuals with a subclavian lesion, a localized thrill can be felt over the anterior chest, just below the clavicle, and a localized bruit is frequently evident. Occasionally, a patient is seen in whom collateral venous drainage has compensated for the central venous stenosis. In these cases, there is no edema present within the field of venous drainage. However, a marked proliferation of collateral veins on the neck, thorax, and abdomen may be obvious.

Aneurysms/pseudoaneurysm — Aneurysms and pseudoaneurysms are characterized by a bulging enlargement of the access at least three times the diameter of the AV access [16]. An AV fistula aneurysm is a focal dilation of the access that involves the layers of the vessel as well as the subcutaneous tissue and skin. Pseudoaneurysms are associated with a defect in the vessel wall such that the bulging enlargement consists only of fibrous tissue, subcutaneous tissue, and skin outside the vessel wall. These can occasionally occur in the AV fistula. If either an aneurysm or pseudoaneurysm is present, it should be monitored regularly by physical examination to determine if it is increasing in size and if it is at risk for rupture. If the skin over the lesion cannot be pinched, elective surgery for repair is advised. If there are ulcerations or spontaneous bleeding associated with the site, the patient should be referred for emergency surgery. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Aneurysm/pseudoaneurysm/megafistula'.)

Infection — The AV fistula is less susceptible to the development of infection compared with an AV graft, but infection can occur. This serious complication can be easily recognized by physical examination.

●Superficial infection is associated with needle puncture sites and consists of small pustules, which can be managed with local treatment.

●Deep infection is typically characterized by pain, swelling, erythema, and fluctuance spreading outward and in a circumferential manner and requires surgery [5,17].

Distal ischemia associated with AV access — The temperature of the ipsilateral hand should be compared with the contralateral hand. Often, in the hemodialysis patient, both hands are cool; however, if this finding is limited to only the ipsilateral hand, it suggests hand ischemia (ie, hemodialysis access-induced digital ischemia [HAIDI], also known as dialysis access-related steal syndrome [DASS]). HAIDI is frequently accompanied by complains of pain, which may be either only with hand exercise or during dialysis, or constant. The presence of cyanosis, pallor, nail changes, and ulceration of fingertips is indicative of a higher grade of hand ischemia [2,14]. The presence of a nerve palsy affecting the hand and wrist should raise the suspicion of ischemic monomelic neuropathy [3,18]. While this invariably affects all three nerves to the hand (median, radial, and ulnar), it may have the primary appearance of a mononeuropathy typical of any of these three nerves. (See "Hemodialysis access-induced distal ischemia".)

Detection of accessory vein — Tributaries associated with an AV access may be either accessory veins or collateral veins. Accessory veins represent normal anatomy and are seen almost exclusively with a radial-cephalic AV fistula. A collateral vein is associated with downstream stenosis. While most accessory veins do not cause a problem, large ones can be problematic. Frequently, these veins are visible and may have already been detected by inspection. The purpose of the sequential occlusion test is to detect or confirm its presence and identify its location [12]. This test is similar to the pulse augmentation test (see 'Pulse augmentation test' above), except the focus is upon the disappearance of the thrill at the anastomosis with occlusion of the AV fistula.

The test is performed by occluding the AV fistula a short distance above the anastomosis with one hand while feeling for the presence of the thrill at the anastomosis with the other (figure 7). Because the presence of a thrill depends on access blood flow, thrill will disappear when the access is occluded unless there is an ancillary outflow channel (side branch) between the point of occlusion in the anastomosis. The test is performed by starting a short distance above the anastomosis and sequentially occluding the access by moving the point of occlusion progressively downstream. At any point, if the thrill does not disappear, a side branch is present immediately distal to that point of occlusion.

Detection of direction of flow — It is unusual to have a problem with determining the direction of blood flow when dealing with the typical AV fistula. However, occasionally an AV fistula is created that has bidirectional flow, characterized by antegrade flow in the upper arm and retrograde flow in the lower arm. These accesses can be problematic for the dialysis facility staff and can present confusion when one is cannulating the access in preparation for an interventional procedure.

Direction of blood flow can be easily accomplished by occluding the access with the tip of the finger and palpating on each side of the occlusion point for a pulse (figure 8). The side without a pulse is the downstream (venous) side. The upstream (arterial) pulse will increase in intensity during the occlusion. While it is easier to accomplish this when the patient is not on dialysis, the maneuver can generally be easily performed with needles in place if they are not placed too closely together.

Detection of recirculation — Recirculation occurs when the blood flow of the access falls below the rate demanded by the blood pump. This results in varying degrees of reversal of flow between the needles depending on the severity of the problem. Poor inflow, obstructed outflow, or a combination of the two can result in recirculation. If the degree of recirculation is more than minimal, it can frequently be detected by physical examination.

To test for recirculation by physical examination, the examiner should occlude the fistula between the two needles during dialysis and observe the venous and arterial pressure gauges. However, if the needles have been placed too closely together, this examination will not be possible. With a normal access, very little or no change is observed in either the venous or arterial pressure readings. If recirculation is present and the problem is due to venous outflow, the venous alarm will sound. If it is due to an inflow stenosis, the arterial alarm will sound. When the alarm sounds because pressure limits have been exceeded, the blood pump will quickly stop.

This procedure works because it interrupts the internal flow loop that exists between the two needles and accounts for the access recirculation. If this loop is open, the pressure measurements within the access will remain stable. However, as soon as it is occluded, the pressure measurements will change due to the loss of the recirculation loop. In a normal access, occlusion between the needles will cause no appreciable change in pressure measurements.

Detection of venous hypertension of hand — In addition to symptoms of pain and occasionally swelling of hand, a large prominent vein on the back of the hand should raise suspicion for venous hypertension of the hand (figure 9). Examination of the prominent vein will reveal that it is pulsatile. By occluding the middle of the vein and checking to determine the location of the pulse in the manner used to determine direction of blood flow, one will find that blood flow is retrograde (ie, flowing distally into the hand). It may be possible to see that this vein originates from the anastomosis.

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

●Accuracy of the physical examination – Physical examination of the hemodialysis arteriovenous (AV) fistula is easy and inexpensive. Physical examination has a relatively high degree of accuracy for detecting a dysfunction in a mature AV fistula. Patients should be referred for diagnostic testing as soon as a significant abnormality is detected by physical examination. (See 'Accuracy of physical examination' above.)

●Normal examination – Routine examination should be performed to allow early detection of problems. The evaluation for stenosis should include inspection, palpation, and auscultation of the AV fistula and extremity pulses, seeking to detect any abnormalities. A healthy AV fistula collapses completely with arm elevation and is generally characterized by a diffuse thrill and soft bruit, both with systolic and diastolic components. (See 'Routine examination' above.)

●Commonly encountered problems – The most common complications associated with a mature AV fistula are venous stenosis, arterial stenosis, thrombosis, aneurysm formation, infection, and ischemia. Physical examination of a mature fistula should be systematically directed toward the exclusion of each of these potential problems. (See 'Routine examination' above and 'Detection of specific problems' above.)

•Inflow stenosis – Arterial stenosis may be assessed by evaluating pulse augmentation. The degree of this augmentation is directly proportional to the quality of the fistula inflow. The pulse in a normal fistula will be stronger (augmented) when the fistula is completely occluded a short distance away from the arterial anastomosis. Decreased augmentation suggests stenosis in the juxta-anastomotic region, the anastomosis, or the feeding artery. (See 'Inflow stenosis' above.)

•Outflow stenosis – Venous stenosis is suggested by a strong pulse over the fistula and a localized, accentuated thrill and high-pitched bruit, both of which lack diastolic components. (See 'Outflow stenosis' above.)

•Central venous stenosis – Hemodynamically significant central venous stenosis may manifest as ipsilateral arm edema, which can be massive. Subcutaneous collateral veins are frequently evident over the arm and chest. Pulsation over the fistula is not as strong as it generally is compared with patients with peripheral venous stenosis. A localized thrill may be felt over the anterior chest, just below the clavicle, and a localized bruit is frequently evident. (See 'Central vein stenosis' above.)

•Infection – Superficial infections appear as small, pustular lesions with minimal or no inflammation, swelling, or pain. Deep infections manifest with erythema, swelling, tenderness, and purulence. The AV fistula is frequently tender to touch, although pain is variable. The area generally feels warm, but this is not a very reliable sign, because the skin overlying a flowing fistula is usually warmer than normal. (See 'Infection' above.)

•Aneurysm – Areas of bulging associated with the AV fistula are generally manifestations of an aneurysm. Aneurysm(s) should be monitored by physical examination at the time of each dialysis treatment. A rapidly enlarging bulge is a sign for concern. The overlying skin should be examined for evidence of marked thinning, ulceration, or spontaneous bleeding. (See 'Aneurysms/pseudoaneurysm' above.)

•Hand ischemia – A mildly ischemic hand due to dialysis ischemic steal syndrome appears pale or cyanotic and feels cool to the touch. The radial pulse is generally diminished or absent. Occlusion of the fistula may either increase the strength of a previously weak radial pulse or result in the appearance of a previously absent pulse. In severe cases, ischemic changes of the skin are present, particularly at the fingertips. Ischemic monomelic neuropathy presents immediately after surgery as neurologic dysfunction (manifested by pain, paresthesias, numbness, and motor weakness) in the absence of significant ischemic changes in the tissues of the hand and fingers. (See 'Distal ischemia associated with AV access' above.)