Diagnostic ultrasound ( PDFDrive )

464 PART II Abdominal and Pelvic Sonography
A
B
FIG. 12.37 Inferior Vena Cava (IVC) Filters. (A) IVC ilters can be very dificult to see. Bright linear echoes (yellow arrows) indicate a tine of
the ilter within the IVC (red arrows). This image represents an unusually good visualization of a ilter. (B) Coronal reconstruction of computed
tomography shows the location and form of the ilter. (Courtesy of Anthony Hanbidge, MD.)
sono graphically, cross-sectional imaging with CT or MRI should
generally be recommended to determine the full extent of the
abnormality.
Other Inferior Vena Cava Findings
Dilation of the IVC and hepatic vein oriices is seen in patients
with congestive heart failure. 156
Placement of IVC ilters has become more common. In our
experience, they are inconsistently seen. When seen, ilters appear
as an echogenic foreign body in the IVC. It is rarely possible to
determine more about the ilter than its presence and approximate
location (Fig. 12.37). he IVC may become sclerotic in patients
with long-standing ilters, in whom it may be possible to see an
absence of the IVC along with retroperitoneal collateral veins.
he legs of the ilters can also penetrate the wall of the IVC. his
inding is fairly common on CT and most oten is an incidental
inding, although complications may result. 157 IVC penetration
may be able to be observed sonographically as an echogenic
foreign body extending outside of the IVC.
NONVASCULAR DISEASES OF
THE RETROPERITONEUM
Excepting speciic organs covered in other chapters, ultrasound
is not the primary modality used in deining nonvascular problems
in the retroperitoneum. When the abnormalities described
next are seen sonographically, further cross-sectional imaging
with CT or MRI oten is needed to deine the abnormality
completely.
Solid Masses
Probably the most common solid mass is lymphadenopathy
(enlarged lymph nodes). Causes of nodal enlargement can be
benign or malignant (e.g., infection, lymphoma), but in all cases,
malignancy must be excluded. Lymph nodes are most commonly
hypoechoic. he identiication of a structure as a probable lymph
node is oten by location in a paraaortic or paracaval region or
in the mesentery.
Metastatic disease is another cause of solid masses in the
retroperitoneum. Metastasis most frequently occurs to lymph
nodes but can be seen in other sites. Oten, it is impossible to
tell with certainty whether the mass is nodal or is centered in
some other type of tissue (Fig. 12.38).
Primary malignancies in the retroperitoneum are rare.
he most common malignant retroperitoneal tumor is lymphoma.
158 he next most common are sarcomas: liposarcoma,
leiomyosarcoma, and ibrous histiocytoma. hese tumors generally
undergo surgical resection and have a relatively high rate of
recurrence. 159
Benign masses also occur in the retroperitoneum, including
ibromas, schwannomas, neuroibromas, and lipomas.
Extraadrenal paragangliomas (extraadrenal pheochromocytomas)
are usually benign but can be malignant. 160 he distinction
between benign and malignant retroperitoneal masses cannot
generally be made sonographically, and the inding of an unexpected
mass in the retroperitoneum should generally prompt
further evaluation with CT or MRI.
Fluid collections may also be seen in the retroperitoneum,
including hematoma, urinoma, lymphocele, abscess, and pancreatic
pseudocyst. If well seen and when indicated, sonography
in conjunction with luoroscopy is oten the best way to drain
these collections.
Retroperitoneal Fibrosis
As mentioned previously, retroperitoneal ibrosis is oten grouped
with inlammatory AAA in the disease process called chronic
periaortitis. Retroperitoneal ibrosis can be seen as a mass usually
surrounding the aorta and the common iliac arteries. It can
involve adjacent structures, most oten the ureters, resulting in
displacement of the ureters and oten in obstruction. When related
to AAA, retroperitoneal ibrosis oten regresses with repair of
the AAA.