Diagnostic ultrasound ( PDFDrive )

CHAPTER 12 The Retroperitoneum 457
A
B
C
FIG. 12.29 Stenotic Superior Mesenteric
Artery (SMA) at Distal End of Previously Placed
Stent. (A) Angiogram showing stenosis at the
distal end of a stent. This was treated with balloon
angioplasty. (B) Color and spectral duplex Doppler
ultrasound 3 years later shows extremely elevated
velocity in the SMA. Note the elevation in diastolic
velocity. (C) Gray-scale duplex Doppler image
shows that the stenosis has recurred at distal end
of the SMA stent.
passes between the right common iliac artery and the spine,
where it can become compressed producing May-hurner
physiology (called May-hurner syndrome when it results in
thrombosis). he common iliac veins have major tributaries of
the internal and external iliac veins.
Anatomic Variants
here are three major variations of IVC anatomy, the most
common a duplicated IVC. he duplication is of the infrarenal
portion of the IVC, with incidence of approximately 2%
(Fig. 12.31A). Most oten, the IVC’s let channel enters the let
renal vein. he suprarenal IVC has normal anatomy. he second
most common anomaly is a let IVC (0.5%; Fig. 12.31B), which
also usually drains into the let renal vein. As with a duplicated
IVC, anatomy above the level of the renal veins is normal. With
both these anomalies, the anomalous let-sided segment may
cross the aorta below the level of the let renal vein. Also, the
anomalous segment may cross either anterior or posterior to
the aorta. 129
he third major anomaly is azygous continuation of the
IVC. he infrarenal IVC lows superiorly into the hemiazygos
or azygos veins. he IVC does not course through the liver in
this setting; there is no intrahepatic IVC. he hepatic veins drain
normally into the short suprahepatic (posthepatic) IVC, which
enters the right atrium. Incidence of azygous continuation is
approximately 0.6%. 129
Regarding IVC tributaries, there are variations in the anatomy
of the hepatic veins, let renal vein, and gonadal veins. he
hepatic veins have numerous variations important in preprocedural
planning of liver resection or transplantation. 130 he
most common variation is the presence of an accessory right
hepatic vein. 131
he let renal vein usually passes in front of the abdominal
aorta to join the IVC. It also can be circumaortic (up to 8.7%), 129
where the let renal vein has two branches, one passing behind
the aorta and the other anterior to the aorta. Less oten, it is
retroaortic (up to 2.4%), where a single let renal vein passes
behind the aorta. In both cases, the portion of the let renal vein
passing behind the aorta most frequently descends a short distance
toward the pelvis as it passes behind the aorta. 129
he right gonadal vein joins the IVC just below the level of
the right renal vein or at the right renal vein in 90% of cases. In
the remaining 10%, it joins the right renal vein. When IVC
anatomy is standard, the let gonadal vein almost always drains
into the let renal vein. In a duplicated or let IVC, the let gonadal
vein most oten drains into the let-sided IVC. 132