Authors (year)
Number of patients enrolled
Confirmatory test
Location of stenosis
Sensitivity (%)
Specificity (%)
Asif et al. [3] (2007)
142
Angiography
Inflow
85
71
Outflow
92
86
Campos et al. [4] (2008)
84
Doppler ultrasound
Presence of stenosis
96
76
Tessitore et al. [13] (2011)
119
Angiography
Inflow
70
76
Outflow
75
93
Coentrao et al. [6] (2012)
177
Angiography
Inflow
98
88
Outflow
97
92
The Physical Examination
Inspection
Quick examination of an access and surrounding areas will reveal many clues of underlying problems. The skin overlying the fistula should be without signs of infection, bleeding, dermatitis, or aneurysmal dilatation. The arm and hand should be without edema. The cannulation sites should be well healed with minimal to no scabbing. As discussed below, observation of collapse of a dilated fistula upon raising the arm, the Arm Raising Test, is normally present, and a lack of collapse may suggest outflow stenosis. The arm, chest, neck, and face should be examined for presence of edema or dilated collateral veins, which may suggest outflow stenosis in the cephalic arch or central veins. Examination of entire extremity including the hands should demonstrate absence of skin changes, swelling, and abnormal coloration.
Palpation and Auscultation
These are used to find new diagnostic findings as well as to confirm findings of inspection. The fistula is expected to be soft, compressible, and generally distended somewhat when the patient’s fistula arm is dependent position but should collapse if the arm is elevated to a level above that of the heart (Arm Raising Test). Examples of palpation include that palpation of a hard nodule, expression of pus from infected access, temperature of skin, palpation of pulses in the distal arm, and evaluation of edema.
Thrill, Bruit, and Pulse
Palpable buzz (thrill) and the auscultated sound (bruit) are a result of turbulent blood flow with eddy currents through the vascular access and can be used to diagnose underlying access problems, locations, and severity. The thrill is best evaluated using the palm of the hand, rather than the fingers. The thrill should be palpable over the length of the fistula but most pronounced over the anastomosis. The nature of the pulse at various sites is also very helpful in delineating problems with the access. In general terms, a thrill is more related to inflow of blood into the access than outflow, while pulse reflects the outflow of the blood. The thrill and pulse disappear with complete thrombosis or stenosis. These examinations are performed both unaugmented, that is, without any digital pressures on the access, and with augmentation, after application of digital pressure on various sites of the access:
- (a)
Thrill and bruit: Good flow through the access is associated with strong thrill/bruit throughout the access and is present during the entire cardiac cycle (both the systole and diastole). As blood flow decreases, either due to stenosis or thrombus, the thrill/bruit becomes weaker. With further decreased flow due to significant obstruction, the thrill/bruit is felt/heard only during systole, becoming weaker or disappearing as flow becomes even slower. Change in the nature of thrill/bruit will reflect flow into the fistula and will change with augmentation as discussed below.
- (b)
Pulse: Palpation of pulse on the hemodialysis access is commonly utilized. Pulse indicates resistance to blood flow downstream from palpitation point. In a normal AVF, the pulse is generally soft and easily compressible. A hyperpulsatile hard pulse indicates increased resistance such as presence of stenosis downstream from the point of palpation. Palpation could be unaugmented or augmented.
Unaugmented: When blood flow is satisfactory, palpation should reveal strong pulse throughout the AVF. With obstruction the pulse downstream of stenosis becomes weaker; however, upstream from obstruction becomes quite pronounced – often described as “the water-hammer pulse” (Fig. 21.1a).
Augmented: Without any obstruction (stenosis), digital pressure will increase the force of pulse upstream of pressure. The presence of significant stenosis will result in a weak pulse downstream from stenosis, and digital pressure may further weaken it. The pulse upstream from stenosis, however, will already be strong (water hammer) in quality, and digital pressure will not further augment it (Fig. 21.1b).
Fig. 21.1
An illustration of an arteriovenous fistula showing the artery, anastomosis, and body of the fistula. (a) An unaugmented palpation of an arteriovenous fistula with a juxta-anastomosis stenosis causing the pulse downstream of stenosis to become weaker, and the thrill is decreased while the upstream from obstruction the pulse is pronounced (water-hammer pulse). (b) Showing stenosis in the body of fistula. The pulse upstream from stenosis is strong (water hammer) in quality, and digital pressure (augmented palpation) will not increase the water-hammer pulse
Most AVGs are created in standard configuration; however, sometimes an element of creativity is needed in the creation or revision of some AVG. It is important to detect the flow direction in an AVG during the physical examination as the orientation of needles for hemodialysis must correspond to the direction of blood flow to avoid recirculation. This can be easily done by compressing the arteriovenous graft with the tip of the finger and palpating each side of the occlusion for a pulse. The side with the pulse is the arterial of the graft.
Hemodialysis Access Dysfunction Referrals
A detailed history is the first step in hemodialysis access dysfunction assessment. The next section is organized based on the common reasons; a patient with a hemodialysis access is referred to the internationalist for access assessment. Table 21.2 summarizes the frequent complaints that accompany a dysfunctional access. Table 21.3 summarizes the diagnostic elements in the physical examination used in assessing a hemodialysis access.
Table 21.2
Common history elements addressed when assessing a dialysis access
History assessment | Relevance |
|---|---|
Frequent infiltration episodes in a newly established fistula | Failure to mature, access is too deep |
Frequent infiltration episodes in a previously functioning fistula | Poor inflow – arterial or juxta-anastomosis stenosis Poor outflow – venous stenosis |
Dialysis machine alarms (arterial alarm) | Poor inflow – arterial or juxta-anastomosis stenosis |
Progressive arm swelling | Poor outflow – outflow or central venous stenosis |
Dialysis machine alarms (venous alarm) | Poor outflow – outflow or central venous stenosis |
Prolonged bleeding post dialysis | Poor outflow – outflow or central venous stenosis |
Inadequate dialysis clearance | Hemodialysis access recirculation |
Table 21.3
Common diagnostic elements in the physical examination used in assessing a dialysis access
Exam finding | Relevance | |
|---|---|---|
Inflow problems | Weak or absent pulse distal to the AVF or AVG with hand pain | Steal syndrome |
Weak or absent pulse distal to the AVF or AVG with no hand pain, motor or sensory changes | Asymptomatic flow reversal | |
Severe pain but normal pulse immediately after fistula or graft placement | Ischemic monomeric neuropathy | |
Strong thrill for a short distance then thrill is absent | High-grade stenosis at the site of the strong thrill | |
Good thrill that disappears after a short distance | Possibly collateral branches | |
Outflow problems | Arm edema | Indicates venous outflow problems in the outflow vein or central venous stenosis
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