Diagnostic ultrasound ( PDFDrive )

188 PART II Abdominal and Pelvic Sonography
• Patency of main, right, and let portal veins
• Encasement of hepatic artery
• Local and distant adenopathy
• Presence of metastases
Dilation of the higher-order intrahepatic bile ducts with
nonunion of the right and let ducts is the classic appearance of
hilar cholangiocarcinomas 62 (Figs. 6.28 and 6.29). When encountered,
dilated ducts should be followed centrally toward the hepatic
hilum to determine which order of branching (segmental ducts
and higher or right/let hepatic ducts) is involved with tumor.
Tumor extension into segmental ducts bilaterally precludes
resection.
he obstructing tumor is not always visualized by sonography.
Rates of sonographic detection of masses range from 21% to 87%,
with more recent studies showing higher rates. 67-69 When a mass
is not directly visualized, its presence can be inferred based on
the level of obstruction, although this oten underestimates the
tumor extent. 70 Lobar atrophy leads to crowding of the dilated
bile ducts and, if long-standing, a shit in the axis of the liver
caused by hypertrophy of the contralateral side. he atrophy of
the lobe is oten accompanied by obliteration of its portal vein
and precludes its resection. Diferences in lobar echogenicity,
caused by the varying degree of ductal and vascular obstruction
between the two lobes, is an uncommon inding (Fig. 6.30).
he main, right, and let portal veins should all be examined
with both gray-scale and color Doppler sonography. Narrowing
of the right or let portal veins leads to compensatory increased
low in the accompanying hepatic artery; when prominent arterial
signal is noted on color Doppler, the portal venous low should
be carefully examined (see Fig. 6.30). Tumor encasing, narrowing,
or obliterating the main portal vein or the proper hepatic artery
renders the tumor unresectable, unless en bloc resection of the
vessels is contemplated. Detection of the extrahepatic tumor
iniltration and early peritoneal metastases is diicult with
sonography, and CT or MRI is recommended as an adjunct for
preoperative assessment.
Assessment by Contrast-Enhanced Sonography. he
role of contrast is in the assessment of the liver-invasive component
of cholangiocarcinoma, and the diferentiation of
intraductal enhancing tumor from sludge and debris within the
duct. Both the liver-speciic phase of enhancement in agents
that are retained by the reticuloendothelial system and the venous/
delayed phase in agents that remain purely within the intravascular
space are useful in this regard. Depending on the agent, the
delayed or liver-speciic phase of enhancement signiicantly
increases the contrast diference between the liver parenchyma
and invasive tumors that show washout or lack uptake. herefore
the invasive component of cholangiocarcinoma—not seen in a
signiicant minority of patients—becomes visible in most, if not
all, cases 70 (see Fig. 6.23; Fig. 6.31, Videos 6.7 and 6.8). his
improved visibility allows for improved performance of sonography
in the staging of hilar cholangiocarcinomas. 70
Distal Cholangiocarcinoma
Distal cholangiocarcinomas are clinically indistinguishable
from the hilar forms, with progressive jaundice seen in 75% to
90% of patients. 51 Although the nodular-sclerosing subtype still
predominates, polypoid masses are seen more frequently. Surgical
resection is the most efective therapy, so a careful search for
spread that would preclude resection is vital. he tumor may
locally extend cranially within the ducts, even involving the
cystic and right and let hepatic ducts; therefore the superior
extent of the tumor must be clearly deined. he tumor may
also extend beyond the duct walls. Patients may present with a
distal obstructive mass with identical appearance to pancreatic
adenocarcinoma. he status of the adjacent vascular structures
must be determined, including portal and superior mesenteric
veins and common hepatic artery. Spread to lymph nodes adjacent
to the tumor is common. Spread to more distant nodes, such as
celiac, superior mesenteric, and periportal regions may preclude
resection. 51 Surgical approach to a distal cholangiocarcinoma is
a pancreaticoduodenectomy.
On sonography the distal cholangiocarcinoma has a variable
appearance. A polypoid tumor appears as a duct-expanding,
well-deined intraductal mass, oten with no internal vascularity
(Fig. 6.32). he nodular-sclerosing tumor causes focal
irregular ductal constriction and duct wall thickening. In more
advanced disease the tumor appears as a hypoechoic, hypovascular
mass with poorly deined margins invading adjacent
structures.
Metastases to Biliary Tree
Metastases to the biliary tree mimic the varied appearance of
cholangiocarcinoma, afecting both the intrahepatic and extrahepatic
ducts (Fig. 6.33). he history of past or concurrent
malignancy along with multiple lesions should suggest metastases.
In our experience the breast, colon, and skin (melanoma)
constitute the primary sites of malignancy.
THE GALLBLADDER
Anatomy and Normal Variants
he gallbladder is a pear-shaped organ lying in the inferior margin
of the liver, between the right and let lobes (Fig. 6.34). he
middle hepatic vein lies in the same anatomic plane and may
be used to help ind the gallbladder fossa. he interlobar issure,
the third structure separating the two hepatic lobes, extends
from the origin of the right portal vein to the gallbladder fossa.
his issure has been seen in up to 70% of hepatic ultrasound
studies 71 and may also be used as a landmark for the gallbladder
fossa. he gallbladder is divided into the fundus, body, and neck;
the fundus is the most anterior, and oten inferior, segment. In
the region of the gallbladder neck, there may be an infundibulum,
called the Hartmann pouch, which is a common location for
impaction of gallstones. 11
he gallbladder derives as an outpouching from the embryonic
biliary tree. he proximal portion of the pouch forms the cystic
duct, and the distal portion forms the gallbladder. Within the
cystic duct (and sometimes the gallbladder neck) are small
mucosal folds called the spiral valves of Heister; these are
occasionally identiied on sonography. During its initial development,
the gallbladder lies in an intrahepatic position, but as it