Physical examination of the arteriovenous graft

INTRODUCTION — Physical examination of the hemodialysis arteriovenous (AV) graft is easy, inexpensive, and detects the common problems associated with dialysis vascular access [1-5]. For this reason, the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) Clinical Practice Guideline for Vascular Access: 2019 Update recommends that clinicians involved in the care of a hemodialysis patient be trained in physical examination of the AV access to detect AV access dysfunction [6]. The basic principles are easily learned and are similar to those for examining an AV fistula; however, physical examination of the AV graft is not as sensitive as performed on a fistula for the detection of stenotic lesions and flow-related dysfunction [7]. Nevertheless, it is a good technique for detecting significant clinical problems and should be performed.

This topic review provides a guide to the physical examination of the AV graft. Physical examination of the AV fistula is discussed separately. (See "Early evaluation of the newly created hemodialysis arteriovenous fistula" and "Physical examination of the mature hemodialysis arteriovenous fistula".)

ACCURACY OF PHYSICAL EXAMINATION — The accuracy of the physical examination of the arteriovenous (AV) graft for the detection of problems is variable and depends upon the experience of the clinician; however, the necessary clinical skills can be taught and do improve with time and practice [2,3,5,7-13]. Physical examination is less effective for diagnosing stenosis in AV grafts compared with AV fistulas. With AV grafts, outflow stenosis is more easily detected than inflow stenosis, likely related to the subjectivity in interpretations of pulse augmentation, but individual accuracy can improve. Importantly, the detection of many of the problems that affect AV grafts such as pseudoaneurysms, infection, and distal ischemia is easily learned.

Physical examination has a moderate sensitivity for detecting stenosis [14]. In a reported series of 328 AV grafts, among patients who were screened first with a physical examination, there was a 92 percent incidence of significant (>50 percent) venous stenosis detected by angiography [13]. For the detection of vein-graft anastomotic stenosis, sensitivity and specificity was 57 and 89 percent, respectively, among 43 patients referred for AV graft dysfunction [14]. Physical examination is less accurate for the detection of intragraft and inflow stenoses [14]. The sensitivity and specificity for the intragraft lesion was 100 and 33 percent; for inflow stenosis it was 73 and 73 percent, respectively. Physical examination had a sensitivity of 16 and specificity of 100 percent for the detection of central vein stenosis. The patients in this study with a central lesion were asymptomatic.

Further diagnostic testing — In general, a stenotic lesion associated with an AV graft that produces abnormalities detectable by physical examination is likely to be significant enough to warrant evaluation by diagnostic imaging in preparation for treatment. The development of any such lesion, whether related to inflow or outflow, increases the risk of AV graft dysfunction, which can result in inadequate dialysis and eventually thrombosis and potential loss of the AV graft.

Diagnostic imaging is usually in the form of ultrasound or angiographic imaging. Ultrasound can be used to better define the problem and is a more appropriate initial imaging modality since it is noninvasive. Angiography, while the gold standard for defining any vascular problem, should only be performed as a prelude to anticipated treatment. Stenotic lesions associated with significant access dysfunction can be treated by endovascular means with a high expectation of success [15].

ROUTINE EXAMINATION — The KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update recommends that regular physical examination of the arteriovenous (AV) graft be performed by a knowledgeable and experienced health practitioner to detect flow dysfunction of the access [6]. To facilitate this, we believe that the AV graft and overlying skin should be examined at every hemodialysis treatment and followed up with a detailed physical examination of the access if any clinical abnormalities are present, such as arm swelling, prolonged bleeding after the needles are pulled, poor blood flow, or difficulty with cannulation. This requires that all clinical staff that are directly involved in the care of hemodialysis patients be familiar with the basic techniques utilized in the examination of an AV graft. Routine physical examination of the AV graft by the dialysis staff allows for early detection of the major problems that are commonly associated with AV accesses, thus avoiding missed treatments and emergency situations. (See "Clinical monitoring and surveillance of hemodialysis arteriovenous grafts to prevent thrombosis" and 'Detection of specific problems' below.)

Routine examination should incorporate three components: inspection, palpation, and auscultation. This evaluation should involve the entire extremity, including the AV graft.

Inspection — The first step in a systematic evaluation is inspection of the AV graft and the overlying skin. The skin should be intact and normal in appearance without areas of discoloration (erythema, bruising, depigmentation). Cannulation sites should be well healed with minimal to no scabbing and no evidence of inflammation or infection (erythema, pustules, swelling, fluctuance).

The graft should be examined for areas of bulging (ie, localized dilation of the graft). These generally represent the development of a pseudoaneurysm. This could be acute if not present on the previous examination or chronic if not a new discovery. If bulging is present, the skin overlying the area should be examined for evidence of thinning, ulceration, or spontaneous bleeding. (See 'Pseudoaneurysms' below.)

A dermal flare can occasionally be seen immediately following AV graft placement and should not be confused with infection. It is characterized by erythema that does not spread in a circular fashion but is restricted to the skin immediately overlying the entire course of the graft. Unlike infection, there is generally little to no swelling, no pustules, no fluctuance, and no pain or tenderness other than the expected postsurgery discomfort. (See 'Infected graft' below.)

The hand ipsilateral to the AV graft should be compared with the contralateral, presumably normal, hand and should be similar in appearance without evidence for ischemia (ie, not be cooler or paler than the normal hand). The entire extremity, including the shoulder and anterior chest, should also be examined for any evidence of venous collateralization that might suggest central venous outflow obstruction. There should be no edema of the extremity. Generalized edema of the extremity suggests the presence of central vein stenosis.

Palpation — The normal hemodialysis AV graft should be relatively soft and compressible, and palpation should not elicit any pain. The skin overlying a flowing graft is always slightly warmer than the surrounding area. The skin overlying the graft should be intact. With chronic use, graft defects can develop in areas of frequent cannulation (failure to rotate cannulation sites). These can be detected by palpation. In the area of the defect, the sides of the graft can be detected with no intervening graft material (railroad track deformity).

Pulse — Changes in the pulse of an AV graft are not as obvious as in an AV fistula due to the lack of compliance in the graft material. Nevertheless, the pulse in the AV graft should be evaluated along its entire length from the arterial to the venous anastomosis. The pulse may be best appreciated using the fingers. In general, the AV graft should have little pulse. The pulses in the draining veins should also be evaluated. These veins should be soft and easily compressible with little pulse. It should be recognized that a pseudoaneurysm will always have increased pulsatility because of Bernoulli principle. According to this principle, when fluid is flowing through a cylindrical object that varies in diameter (such as a normal vessel that feeds into an aneurysm), the changes in diameter result in changes in velocity. Thus, where the velocity is lower (eg, as in an aneurysm), the pressure exerted on the wall is greater in comparison with that in the zone where the velocity is higher (eg, as in a normal vessel).

Pulse augmentation — When the examiner manually occludes the outflow vein of a normal AV graft some distance away from the arterial anastomosis, the pulse in the graft, between the occlusion point and arterial anastomosis, should increase or become augmented (the "pulse augmentation" test). The degree of this augmentation is directly proportional to the quality of the arterial inflow. It is very useful to develop the practice of grading pulse augmentation (0 [absent], 1+ [diminished], 2+ [normal]). If the augmentation is judged to be diminished, it represents poor inflow to the access. It only takes minimal experience with this evaluation for one to begin to recognize what is normal and what is abnormal. This evaluation cannot be accomplished while the patient is on dialysis.

Thrill — A thrill, often referred to by patients as a "buzz," is a palpable vibration felt over the AV graft that is related to flow. Thrills are best evaluated using the palm of the hand. The normal AV graft is characterized by a soft, continuous, diffuse thrill that is generally palpable to some degree over the entire course of the graft. It should have both a systolic and diastolic component. However, these components may be difficult to distinguish due to the rigidity of the graft material. The thrill is generally locally accentuated at the arterial anastomosis. Any other localized accentuation of the thrill should be noted (abnormal suggests stenosis). The entire course of the draining veins, including the subclavicular and supraclavicular areas, should also be examined for abnormal thrills.

Direction of flow — At least once before initiating dialysis, the direction of blood flow in the AV graft should be determined and documented for each patient in the dialysis facility by occluding the graft with the finger or a blunt object (side of a hemostat) and determining which side of the occlusion is pulsatile. The side without a pulse is the downstream side (ie, in the direction of flow). The upstream (arterial) pulse will increase in intensity during this occlusion. While it is easier to accomplish this when the patient is not on dialysis, the maneuver can generally be adequately performed with needles in place, if they are not placed too closely together.

Auscultation — Auscultation of the hemodialysis AV fistula can be performed using a stethoscope or with a handheld Doppler. One advantage of using Doppler is the ability to detect very low flow that distinguishes an AV graft that has a severe stenosis from one that is completely occluded. (See 'Thrombosed graft' below.)

Bruit — A bruit is the auditory manifestation of a thrill and has the same significance as the thrill. A bruit is characterized by both its auditory frequency (pitch) and its duration. The bruit over a well-functioning AV graft has a low-pitched, soft, machinery-like rumbling sound and, like the thrill, has both a systolic and diastolic component. However, these components are generally more easily detected in the bruit. The bruit is also accentuated at the arterial anastomosis.

DETECTION OF SPECIFIC PROBLEMS — The most common complications associated with an arteriovenous (AV) graft are venous stenosis (peripheral, central), arterial stenosis, thrombosis, infection, pseudoaneurysm formation, and hand ischemia. Physical examination of the graft should be systematically directed toward the detection of these potential problems. Physical examination of the AV graft should lead the examiner to the specific site of the problem. When evaluating the pulse, thrill, or bruit, one has to be careful not to create artifact by compressing the AV graft with the examining hand or fingers.

Stenotic vascular lesions — Stenosis is the most common complication affecting the hemodialysis AV access. The AV graft is part of a vascular circuit that begins and ends with the heart. Stenosis may occur anywhere along this hemodialysis circuit (ie, the arterial side, the AV graft itself, or the venous side).

Recirculation as a sign of stenosis is uncommon with an AV graft because thrombosis generally occurs before blood flow drops low enough to be associated with this phenomenon. Nevertheless, occasional patients may require evaluation for recirculation [16]. (See "Arteriovenous fistula recirculation in hemodialysis".)

Intragraft or venous outflow stenosis — A strong pulse in the AV graft (hyperpulsatility) suggests an increase in downstream (ie, in the direction of flow) resistance as occurs with a venous stenotic lesion (figure 1). The intensity of this pulse is directly proportional to the severity of the stenosis. For this reason, hyperpulsatility in an AV graft should be considered an adverse finding.

Narrowing of the vein or graft lumen produces a localized, accentuated thrill due to turbulent flow occurring at that point. The most common site is stenosis at the AV graft venous anastomosis. Additionally, due to the increased resistance that occurs, the diastolic component of both the thrill and bruit become increasingly shortened as the stenosis progresses. With severe stenosis, the thrill and bruit may become completely absent. The pitch of the bruit increases as the severity of the lesion increases. With severe downstream stenosis, the bruit may become a high-pitched, almost whistling sound that is heard only during systole.

Arm elevation tests, which are commonly performed to evaluate for venous stenosis in a fistula, are not effective for the evaluation of venous stenosis in a synthetic graft due to the higher levels of intra-access pressure that are present. (See "Physical examination of the mature hemodialysis arteriovenous fistula", section on 'Arm elevation test'.)

Arterial stenosis — Reduced pulse augmentation (less than 10/10) suggests inflow stenosis due to stenosis of the arterial anastomosis or of the feeding artery. Although pulse augmentation is commonly performed, it is less sensitive for the detection of inflow stenosis in grafts compared with fistulas. (see 'Pulse' above)

Central vein stenosis — The physical findings of central venous stenosis differ from those of venous stenosis in the hemodialysis access or peripheral veins. The classic physical finding in a patient with a significant central venous stenosis is diffuse upper extremity edema, which can be massive. Subcutaneous collateral veins are frequently evident over the arm and chest. Swelling and collateral veins are caused by generalized venous hypertension of the extremity, which occurs in central but is rare with peripheral lesions. Not all central venous lesions are hemodynamically significant [2,10]. Many are asymptomatic and undetectable by physical examination. However, diffuse swelling of the extremity, even if not massive, or the development of chest wall collaterals suggests a clinically significant central venous lesion. In spite of a significant outflow stenosis, the pulsation over the AV graft is generally minimal and frequently not apparent. It is not hyperpulsatile as in peripheral venous stenosis because the pulse is dampened by the intervening veins between the AV graft and the central stenosis. Often, especially in thin-chested individuals with a cephalic arch or subclavian lesion, a localized thrill and bruit can be detected over the anterior chest, just below the clavicle.

Thrombosed graft — There are no particular physical findings that are unique for thrombosed AV graft other than what would be expected: a silent graft. Decreasing flow in an AV graft due to a significant venous stenosis causing increased outflow resistance, or due to reduced arterial inflow, will eventually lead to AV graft thrombosis. The typical clinical scenario is abrupt thrombosis, at times with only moderate degrees of stenosis.

Infected graft — Dialysis graft-associated infection may be either superficial or deep. (See "Arteriovenous graft creation for hemodialysis and its complications", section on 'Graft infection' and "Arteriovenous graft creation for hemodialysis and its complications" and "Arteriovenous fistula creation for hemodialysis and its complications".)

●Superficial infections do not involve the AV graft itself and are generally related to previous cannulation sites. On physical examination, superficial infections appear as small pustular lesions. If there is significant erythema, swelling, fluctuance, tenderness, or pain, progression to a deep infection should be suspected.

●Deep infections are manifested by erythema, localized swelling, tenderness, and purulence. The erythema is generally localized to the skin overlying the infected site and spreads outwardly. The area is frequently tender to touch; pain may be present but is variable. The area generally feels warm, but this is not a very reliable sign because the skin overlying a flowing graft is always warmer than normal. Deep infections are frequently associated with pustular lesions and purulent drainage and may be fluctuant to palpation. Occasionally, infection-associated anatomic abnormalities such as aneurysms, perigraft hematomas, or an abscess from an infected needle puncture site may be observed.

Rarely seen is a condition referred to as a dermal flare, which is associated with a newly placed AV graft and is made apparent by the presence of incisions that have not yet healed [6,17]. This must be distinguished from infection. This typically involves the entire course of the access, which is characterized by erythema that is localized to the course of the graft and does not spread outward. This contrasts with cellulitis, which is more diffuse and associated with pain and tenderness.

Pseudoaneurysms — An AV graft can develop an area of localized bulging or dilation. These represent a pseudoaneurysm (false aneurysm), which is due to disruption in the wall of the graft. Two problems are generally required for the development of these lesions: a graft defect (repetitive cannulation in same area) and increased intra-access pressure (downstream stenosis). A newly developed pseudoaneurysm should be immediately investigated to arrest further enlargement. Chronic pseudoaneurysms should be monitored by physical examination at the time of each dialysis treatment. (See "Arteriovenous graft creation for hemodialysis and its complications", section on 'Pseudoaneurysm'.)

The skin overlying a chronic pseudoaneurysm should be examined for evidence of marked thinning, ulceration, or spontaneous bleeding. In interpreting the significance of skin changes, one should keep in mind that the AV graft has relatively high pressure, and the wall of the pseudoaneurysm does not include graft material. It is composed only of skin and a small thickness of subcutaneous tissue. If the integrity of this thin covering layer becomes compromised, rupture can result in significant hemorrhage. Any ulceration or spontaneous bleeding is an indication for emergent surgical treatment. To evaluate the degree of thinning of the skin, the "pinch test" is recommended. If you cannot pinch the skin overlying the pseudoaneurysm, it is too thin and at risk of rupture. The lesion should be addressed surgically as early as possible. Depigmentation of the skin may also be evident but has no particular significance other than its association with thinning of the skin.

Distal ischemia associated with AV access — Placement of an AV graft can cause hand ischemia.

●Hand ischemia (dialysis access steal syndrome [DASS]) is not as common with an AV graft as with an AV fistula, and if it does occur, it is most likely to occur immediately after AV graft placement [18]. Physical findings associated with DASS vary according to the severity and duration of the problem. In most instances, it is very helpful to compare the affected side to the opposite, presumably normal or relatively normal side. In the mildest cases, the affected hand is pale or cyanotic in appearance and feels cool. In more severe cases, ischemic changes of the skin, especially at the fingertips, can be present, and the patient generally has significant pain and neuropathic changes. The ipsilateral radial pulse is nearly always diminished or absent. Occlusion of the access may be found to either increase the strength of a previously weak radial pulse or result in the appearance of a previously absent pulse and may relieve the painful symptoms temporarily. Using a Doppler to listen to the bruit over the vessel frequently aids in this examination. The sound is significantly augmented when the access is occluded. In some cases, the volume of the radial pulse may be normal on palpation, even though the patient demonstrates DASS [18]. (See "Hemodialysis access-induced distal ischemia".)

●Ischemic monomelic neuropathy (IMN) can also occur, primarily in diabetics, following the placement of an AV graft if the brachial artery has been used. The symptoms of the neuropathy include pain, paresthesias, numbness, and weakness of the muscles of the hand, wrist, and forearm. The sensory deficits are frequently more prominent than the motor deficits. Typically, the hand is warm and generally has a palpable radial pulse or audible Doppler signal. Symptoms occur in the distribution of the three forearm nerves along with some degree of motor weakness or paralysis: weak wrist extension (radial nerve), weakness of the intrinsic hand musculature (ulnar nerve), or weakness in thumb opposition (median nerve). On physical examination, the patient may present with what appears to be a mononeuropathy of any one of the three involved nerves, but IMN is always a polyneuropathy, with variable degrees of individual nerve involvement. Evidence that only a single upper limb nerve is involved should bring the diagnosis into serious question [18]. (See "Hemodialysis access-induced distal ischemia", section on 'Differentiating IMN from DASS'.)

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 provides a reasonably accurate screening test for AV graft stenosis, although it is not as accurate compared with detection of stenosis in AV fistulas. Patients should be referred for diagnostic testing whenever a significant abnormality is detected by physical examination. (See 'Accuracy of physical examination' above and 'Further diagnostic testing' above.)

●Normal examination – A systematic physical examination of an AV graft should be performed at regular intervals to allow early detection of AV graft problems. This requires that all clinical staff who are directly involved in the care of hemodialysis patients are familiar with the basic techniques used in the examination of an AV graft. The evaluation for stenosis should include examination of the pulse and the detection of an abnormal thrill and bruit. A healthy AV graft is generally characterized by a soft, diffuse thrill and soft bruit, both with systolic and diastolic components. (See 'Routine examination' above.)

●Commonly encountered problems – The most common problems associated with an AV graft are venous and intragraft stenotic lesions, inflow (arterial) stenosis, thrombosis, pseudoaneurysm formation, infection, and ischemia. Physical examination of the AV graft 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 inflow stenosis may be assessed by evaluating pulse augmentation with complete occlusion of the graft a short distance away from the arterial anastomosis. The pulse over a normal AV graft is augmented by this maneuver. The degree of this augmentation is directly proportional to the quality of the arterial inflow. Decreased augmentation suggests inflow stenosis, which may be due to stenosis of either the arterial anastomosis or the feeding artery. (See 'Arterial stenosis' above.)

•Outflow stenosis – A venous stenosis is suggested by a strong pulse over the graft (ie, hyperpulsatility) and by a localized, accentuated thrill and a high-pitched bruit, both of which may lack diastolic components. (See 'Intragraft or venous outflow stenosis' above.)

•Central venous stenosis – Hemodynamically significant central venous stenosis may manifest as diffuse ipsilateral arm edema, which can be massive. Subcutaneous collateral veins are frequently evident over the arm and chest. Increased pulsation over the graft is not as strong as it generally is among patients with peripheral venous stenosis. A localized thrill may be felt over the anterior chest, just below the clavicle, and a localized bruit may be evident and, if present, is indicative of subclavian stenosis. The same findings in the absence of arm edema could be either subclavian vein or cephalic arch stenosis. (See 'Central vein stenosis' above.)

•Infection – Superficial infections appear as small, pustular lesions, with minimal or no inflammation, swelling, or pain. Deep infections are manifested by erythema, swelling, tenderness, fluctuance, and purulence. The AV graft 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 graft is always warmer than normal. In the recently placed AV graft, infection must be distinguished from a dermal flare. (See 'Infected graft' above.)

•Pseudoaneurysm – Areas of bulging associated with the AV graft are generally manifestations of a pseudoaneurysm. Pseudoaneurysm(s) should be monitored by physical examination at the time of each dialysis treatment. A rapidly enlarging bulge is cause for concern. The overlying skin should be examined for evidence of marked thinning, ulceration, or spontaneous bleeding, the occurrence of which should be treated as an urgent situation. (See 'Pseudoaneurysms' above.)

•Hand ischemia – A mildly ischemic hand due to steal syndrome appears pale or cyanotic and feels cool to the touch. In more severe cases, ischemic changes of the skin, especially at the fingertips, are present and frequently associated with pain. Manual occlusion of the AV graft may diminish the pain. Ischemic monomelic neuropathy presents 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.)