Diagnostic ultrasound ( PDFDrive )

CHAPTER 27 Peripheral Vessels 1003
A
B
FIG. 27.59 Accessory Arteriovenous Fistula (AVF) Branch Measurement. (A) Transverse image of the AVF draining vein (*) shows a branch
of 0.24 cm (cursors). (B) Larger accessory AVF branch (cursors) of 0.44 cm may be large enough to sump blood away from the AVF draining vein
(*).
FIG. 27.60 Volume Flow in a Fairly Straight Area of an Arteriovenous
Fistula (AVF) Draining Vein.
be inspected for echogenic foci or gas. Fluid collections with
echogenic foci associated with shadowing suspicious for gas may
represent abscess in certain clinical settings.
Aneurysm and Pseudoaneurysm. Focal or difuse aneurysmal
dilation of the AVF draining vein may occur as a result
of repeated puncture (Fig. 27.63). Pseudoaneurysms may develop
within a istula or grat and oten are related to suboptimal
compression ater cannulation. Color Doppler of a pseudoaneurysm
reveals a circular low pattern termed “yin-yang” (Fig.
27.64, Video 27.27). here may be “to-and-fro” low identiied
in the pseudoaneurysm neck. Evaluation of the depth of the
anterior wall of the pseudoaneurysm from the skin surface is
important to evaluate those pseudoaneurysms in danger of
imminent rupture. A unique complication of grats is the
degeneration of grat synthetic material. Irregularity of the grat
wall is present, which may be associated with difuse or focal
pseudoaneurysms along the length of the grat wall (Fig. 27.65,
Video 27.28).
Arteriovenous Fistula Maturation Evaluation
A 6-week postoperative AVF ultrasound is used in some clinical
centers for routine evaluation of the AVF to determine its
development toward usability. 130 A functioning AVF has a volume
low of at least 300 to 800 mL/min. 129,151 Robbin and colleagues
showed that when an AVF had a minimum draining vein of
4 mm or larger or a blood low rate of 500 mL/min or higher,
approximately 70% of AVFs were able to be used for hemodialysis.
he likelihood of istula maturation was 95% if both criteria
were met. If neither of these criteria was met, only 33% of istulas
were used for hemodialysis. 129 Sonographic criteria published
by the National Kidney Foundation Kidney Disease Outcomes
Quality Initiative suggestive of maturation include a draining
vein greater than 6 mm diameter, blood low rate greater than
600 mL/min, and less than 6 mm skin depth. hese criteria may
exclude many istulas that could subsequently provide hemodialysis
access. Active investigation is underway with larger,
multicenter trials to test these criteria. Etiology of failure to
mature such as anastomotic or AVF draining vein stenosis, large
accessory veins, or arterial inlow stenosis can be identiied and
ultrasound used to triage the AVF for intervention. 131
Arteriovenous Fistula and Graft Stenosis
AVF. Stenoses associated with AVFs are most frequently
juxta-anastomotic, followed in frequency by AVF draining vein,
with central venous and feeding artery stenosis less common
but not infrequent. Stenoses may be clinically relevant owing to
resultant low decrease and can be associated with subsequent
thrombosis. Potential sites for AVF stenosis include the feeding
artery, juxta-anastomotic region, draining vein, and central veins.
Early ater placement, juxta-anastomotic stenoses are the most
common. Later, AVF draining vein and central vein stenoses are
more common, including a “cephalic arch” stenosis in which the
cephalic vein enters the subclavian vein in the cephalic vein AVF.
A careful directed search to common areas of stenosis is important
during the sonographic examination, because stenoses may be
short and therefore overlooked.
Fistula stenosis is characterized by two criteria: (1) visual
narrowing of greater than 50% as assessed on gray-scale
imaging, and (2) an elevated PSV ratio of the PSV at or just
distal to the stenosis as compared with the PSV measured
2 cm upstream from the site of stenosis. A juxta-anastomotic
stenosis is deined by a location within 2 cm of the anastomosis,
encompassing both the feeding artery and the draining