Role of USG in A-V fistula assessment

Group Discussion
Presenter :
Dr. Durga Singh (JR1)
Moderator :
Prof. Dr. Sunil Kumar
AV Fistula & USG

AV
Fistula
Ultrasound evaluation before and after
hemodialysis access
• USG / Physical examination / conventional venography
• AV Fistula >>> AV graft
• Pre-operative vascular mapping - increased
visualization of veins , AVFs , success , cause of immature
AVF , treatment of failed AVF

AV
Fistula
AV Fistula
A native AVF is a surgically created , direct
anastomosis b/w an artery & a vein , placed in
either the forearm or upper arm

AV
Fistula
Q1. MC type of fistula is
a. Traumatic
b. Iatrogenic
c. Congenital
d. None
Reference – Bailey and love’s short practice of
surgery
Ans - Iatrogenic

AV
Fistula
AV Fistula
Q2. Distal needle placed in the AVF carries blood –
a. From machine to the pt
b. From pt to the machine
Reference - Chapter 17 , Ultrasound evaluation
before and after hemodialyis access ,
Introduction to vascular ultrasonography -
Zwiebel (5th edition)
Ans - B

AV
Fistula
Types of AV Fistula

AV
Fistula
Types of AV Fistula
Q3. MC type of fistula used for dialysis
is where we join
a. end of vein to end of artery
b. end of vein to side of artery
c. side of vein to end of artery
d. side of vein to side of artery
Reference – Bailey and love’s short
practice of surgery
Ans - B
Brescia – Cimino A-V fistula

AV
Fistula
A-V access for hemodialysis in
preferential order
AV Fistula > AV Graft
Forearm > arm
Non dominant > dominant
Non dominant fistula (FA) - dominant fistula (FA) -
non dominant fistula (arm) – dominant fistula (arm)
non dominant graft (FA>A) - dominant graft (FA>A) –
thigh graft – venous catheter

AV
Fistula
A-V access for
hemodialysis
in preferential
order

AV
Fistula
Vascular mapping prior to hemodialysis
access placement
• Terminology used is proximal/distal or cranial/caudal
• General principles :
1. High resolution linear USG transducer (>-7Hz)
2. Transverse plane : identify vessels ( A/V ) – Diameter ,
wall thickness , compressibility , depth , intimal
thickening , stenosis , concentric calcification
3. Longitudinal plane – C/D , S/D

AV
Fistula
Assessment
1. Subclavian , Internal jugular and Central
Vein Assessment
• Stenosis or thrombosis evaluation
• Spectral waveforms – in medial portion of
subclavian vein and caudal portion of IJV for
respiratory phasicity and transmitted cardiac
pulsatility

AV
Fistula
• Absent flow features – Central venous stenosis or obstruction
• Examine C/L subclavian and IJV
• If flow abnormality is U/L , BCV stenosis / occlusion is likely
• If flow abnormality is B/L , SVC stenosis / obstruction is likely

AV
Fistula
2. Forearm Assessment ( positioning )
• RA diameter at wrist / FA (>-2mm) ND
• UA diameter at wrist / FA (>-2mm)
• RA diameter at wrist / FA (>-2mm) D
• UA diameter at wrist / FA (>-2mm)
IF NO FA ARTERY IS SATISFACTORY – Pt is not a
candidate for forearm AVF

AV
Fistula
• Look for intimal thickening / stenosis /concentric
calcification

• A high RA takeoff from the BA or even AA in the
upper arm is a common anatomic variant. The
presence of this variant can be suspected when two
arteries with accompanying paired veins are seen in the
upper arm. These arteries should be followed into the
forearm, where they assume the respective positions
of the radial and ulnar arteries.
Hemodialysis access surgeons are reluctant to place a
forearm graft or upper arm straight graft in a patient
with a high radial artery takeoff, as the chance for
arterial steal is increased.
Infrequently, a prominent arterial branch that courses
posteriorly toward the elbow can mimic a high radial
artery takeoff. Following the course of the artery more
distally allows differentiation.

AV
Fistula
• It is important to analyze the spectral waveform of the BA
and RA arteries to detect either proximal or distal arterial
obstruction.

AV
Fistula
• It is important to analyze the spectral waveform
of the BA and RA arteries to detect either proximal or
distal arterial obstruction.
With proximal obstruction, the waveforms are
monophasic and dampened.
With distal obstruction, the waveforms have a
normal triphasic pattern, but the velocity may be
reduced because of diminished outflow.

AV
Fistula
• Malovrh noted a higher success rate in FA fistulas in patients
who converted from triphasic to monophasic flow after release
of a clenched fist (Clenched fist maneuver)

Arterial
hyperemic
response – useful
to predict risk of
arterial steal
Clenched fist (3min)
– high resistance flow
(triphasic)
Released fist – low
resistance
(monophasic) and RI
<0.70
Failure of such
response is regarded
as C/I to AVF

AV
Fistula
Modified Allen’s test for patency of palmar arch

AV
Fistula
Q4. Diameter criteria for arteries during fistula mapping for
hemodialysis
a. 5mm
b. 3mm
c. 2.5mm
d. 1.6-1.7mm
Reference - Chapter 17 , Ultrasound evaluation before and after
hemodialyis access , Introduction to vascular ultrasonography -
Ans - D

AV
Fistula
• If RA / UA meets size criteria at wrist / FA - NEXT
evaluate CV
• Tourniquet / percuss for 3 min ---

AV
Fistula
evaluate CV
>2.5mm / continuous upto tourniquet / patency
/compressibilty / wall thickness / depth / follow in
cephalad direction for continuity / stenosis / branch
points/ follow till axilla or subclavian vein (Muscle or
arm position )

AV
Fistula
evaluate CV
>2.5mm / continuous upto tourniquet / patency
/compressibilty / wall thickness / depth / follow in
cephalad direction for continuity / stenosis / branch
points/ follow till axilla or subclavian vein (Muscle or
arm position )
It is possible creating a FA CV AVF , even if the
CV in the upper arm is small or thrombosed. If
the CV in the FA drains into the
brachial or basilic veins via an adequately
sized median cubital or other branch vein, it is
suitable for AVF creation.
Carefully assess vein branch
points, as areas of focal stenosis
may occur at accessory vein
takeoffs. These stenoses may
significantly limit flow in a
subsequently created access.
Depth of the CV from the skin surface should
be measured during the USG mapping
procedure. If the vein is greater than 5mm in
depth, it will likely be difficult to palpate the
vein with sufficient confidence to permit the
insertion of a 15G needle into it for
hemodialysis - SUPERFICIALIZE

AV
Fistula
1. It may be possible to create a FA CV AVF, even if the CV in the upper arm is small or
occluded by thrombus. If the CV in the FA drains into the brachial or basilic veins via
an adequately sized median cubital or other branch vein, it is suitable for AVF
creation.
2. It is important to carefully assess vein branch points, as areas of focal stenosis may
occur at accessory vein takeoffs. These stenoses may significantly limit flow in a
subsequently created access.
3. CV may meet diameter criteria for AVF creation yet may be too deep,to access easily
at hemodialysis once the AVF is mature. Thus, the depth of the CV from the skin
surface should be measured during the USG mapping procedure. If the vein is
greater than 5mm in depth, it will likely be difficult to palpate the vein with sufficient
confidence to permit the insertion of a 15G needle into it for hemodialysis.
Detection of a vein that is too deep but otherwise suitable for an AVF allows the
surgeon to inform the patient preoperatively about the potential need for a second
procedure to "superficialize" the vein in the subcutaneous tissues. This discussion
allows the patient to decide whether to accept the procedure.

AV
Fistula
• If CV is not adeqaute ----
Assess basilic vein ------suitable vein in volar then dosral
surface of FA
>2.5mm / continuous upto tourniquet / patency /
follow in cephalad direction for continuity / stenosis /
branch points/ follow till axilla /drainage point
IF NO VEIN IS SUFFICIENT IN FA – repeat same thing on
dominant side

AV
Fistula
3. Arm Assessment (Nondominant 1st ,
tourniquet at axilla )
• BA diameter at elbow above its bifurcation(>-2mm)
• CV diameter at elbow (>-2.5mm diameter and extend
approx 2 cm below antecubital fossa , evaluate median
cubital branch of CV)
• BV ( 2 cm caudal – transposition or diameter 4mm for
graft / BVs for graft

AV
Fistula
• Suitable vein – Continuity with deep venous system
continuity / adequate diameter / empty point
diameter / continuity / stenosis / branch points/
follow till axilla or subclavian vein

AV
Fistula
Q5. Diameter criteria for veins during graft mapping for hemodialysis
a. 5mm
b. 4mm
c. 3mm
d. 2.5mm
Reference - Chapter 17 , Ultrasound evaluation before and after
hemodialyis access , Introduction to vascular ultrasonography -
Ans - B

AV
Fistula
AVF maturity
assessment

AV
Fistula
AVF maturity assessment
Mature AVF in the United
States is a fistula that is usable
for hemodialysis at a flow of
350 cc/min at six dialysis
sessions in one month.
Practitioners in other
countries, particularly in
Europe, accept lower AVF
flows with subsequently
longer dialysis times.
A mature AVF can be
identified clinically as one
that has a large, easily
palpable vein that can
provide access for two 15-
gauge needles.
If AVF maturity is in doubt ,
use USG (Maturity and
Triage)

AV
Fistula
Sonographic evaluation of
AVF Maturity
• >- 7 Hz
• No tourniquet
• Positioning
• Feeding artery , anastomosis , draining vein
• Transverse plane – vessel diameter , wall thickness ,
compressibility , depth
• Longitudinal plane – C/D , S/D , stenosis , functional
stenosis

AV
Fistula
• The diameter of the draining vein is measured
routinely in the caudal, mid-, and cranial portions of
the forearm, and similarly in the upper arm when a
forearm AVF is evaluated. The entire draining vein
should be scanned, and the minimum diameter
should be measured, even if it occurs at a location
not routinely measured.
• The depth of the anterior wall of the AVF / vein
from the skin surface is also measured (5mm).

AV
Fistula
Blood flow is measured in the AVF in mL/min.
If the blood flow equals or exceeds 500 mL/min, the likelihood of fistula
adequacy is nearly twice as great as with lower flow rates.
Q6. Formula for calculating flow volume in ml/min in a case of A-V fistula is
a. Cross sectional area (cm2) x mean velocity (cm/sec) x 30
b. Cross sectional area (cm2) x mean velocity (cm/sec) x 60
c. Cross sectional area / AT
d. 3.14 x diameter x diameter / 4 (cm2) x mean velocity (cm/sec) x 60
Reference - Chapter 17 , Ultrasound evaluation before and after hemodialyis
access , Introduction to vascular ultrasonography - Zwiebel (5th edition)
Ans – b and d

AV
Fistula
Blood flow is measured in the AVF in mL/min.
If the blood flow equals or exceeds 500 mL/min, the
likelihood of fistula adequacy is nearly twice as great as with
lower flow rates.

AV
Fistula
Combining venous diameter and volume flow
measurement increased our ability to predict
fistula adequacy. A venous diameter of 4 mm or
greater and flow volume equaling or exceeding 500
mL/min confirmed AVF maturity in 95% of cases,
versus a maturity rate of only 33% when neither
criterion is met.

AV
Fistula
KEY ADDITIONAL POINTS REGARDING
AVF EVALUATION :-
1. Look for the presence of large vein branches involving the
first 10cm of the draining vein . These accessory branches
may divert a significant amount of flow from the primary
draining vein with resultant decrease in flow to below
functional levels. Such flow diversion is a frequent reason for
AVF immaturity.These branches can be surgically ligated,
thereby increasing the likelihood that the AVF will mature

AV
Fistula
2. Occasionally, a patient with an AVF may present for evaluation of
arm swelling. Respiratory phasicity and transmitted cardiac
pulsatility should be evaluated in the subclavian and internal
jugular veins, to assess for the possibility of a central venous
stenosis . The brachial veins should also be evaluated for the
presence of deep venous thrombosis.
3. Infrequently, a patient will have symptoms of arterial steal with
an AVF , such as hand pain and numbness, particularly during
dialysis. Flow direction of the distal radial artery is evaluated
using spectral and color Doppler. Arterial steal is diagnosed when
the flow in the radial artery is reversed.

AV
Fistula
Causes of immature fistula –
1. Stenosis at or near the fistula (Angioplasty –
surgical revision)
2. One or more accessory veins (Ligation)
3. Deep draining vein (Fistula surgically placed in
more superficial soft tissues)
Immature fistulas can be converted into usable fistula with
correction of underlying problem

AV
Fistula
Complications of A-V access for
hemodialysis –
1. Stenosis and occlusion
2. Aneurysm and pseudoaneurysm
3. Infected and non infected collections
4. Arterial steal syndrome
5. High output cardiac failure

AV
Fistula
hemodialysis –
Stenosis and occlusion
B mode (diameter reduction)
C/D (aliasing)
S/D ( PSV ratio)

AV
Fistula
• If the draining vein is visibly narrowed, PSV are measured at
the stenosis and 2 cm caudal to the stenosis.
A PSV ratio is calculated by dividing PSV at the stenosis by the
PSV obtained 2 cm caudal to the stenosis.
If the PSV ratio is 2 or more, it is classified as a ~50%
diameter stenosis.
• Both arteriovenous and draining vein stenoses may be
treated with angioplasty or surgical revision.

AV
Fistula
Q7. The most frequent location of AVF stenoses is
a. Draining vein
b. Feeding artery
c. Central veins
d. Perianastomotic
Reference - Chapter 17 , Ultrasound evaluation before and
after hemodialyis access , Introduction to vascular
ultrasonography - Zwiebel (5th edition)
Ans - D

AV
Fistula
PSV is measured at the anastomosis and 2 cm cephalad to the
anastomosis in the feeding artery.
A PSV ratio is then calculated by dividing the PSV at the
anastomosis by the PSV obtained 2 cm cranial to the anastomosis
We generally begin to be concerned about stenosis at the AV
anastomosis when the PSV ratio reaches 3
Visual confirmation of a stenosis at the AV anastomosis is
useful, as the PSV in the draining vein may be significantly
elevated merely because of the acute angulation of the draining
vein at the anastomosis.

PSV at fistula
PSV 2cm cranial to fistula in artery

AV
Fistula
hemodialysis –
Aneurysm and pseudoaneurysm

AV
Fistula
hemodialysis –
Arterial steal syndrome

AV
Fistula
Birectional flow in distal radial artery Restoration of antegrade flow on gentle
compression of fistula

AV
Fistula
Q8. AVF stenosis at the anastomosis site is suspected if the
PSV ratio reaches
a. 1
b. 2
c. 3
d. 4
Ans - c

AV
Fistula
Q9. AVF stenosis in the draining vein is suspected if the PSV
ratio reaches
a. 1
b. 2
c. 3
d. 4
Ans - b

Thank you
By :- Dr Durga Singh

Role of USG in A-V fistula assessment

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Role of USG in A-V fistula assessment