AJR 2003; 180:687-693
© American Roentgen Ray Society
Hilar Biliary Obstruction: Preliminary Results with Levovist-Enhanced Sonography
Korosh Khalili1,
Ur Metser and
Stephanie R. Wilson
1 All authors: Department of Medical Imaging, Toronto General Hospital,
University Health Network, 200 Elizabeth St., Toronto, Ontario, Canada M5G
2C4.
Received January 18, 2002;
accepted after revision August 27, 2002.
Partially supported by Berlex Canada.
Address correspondence to S. R. Wilson.
Abstract
OBJECTIVE. The aim of this study was to investigate the value of
using Levovist in the postvascular phase of sonography performed to assess
hepatic hilar biliary obstruction.
SUBJECTS AND METHODS. In our prospective study, 50 patients
underwent routine sonography followed by postvascular Levovist-enhanced pulse
inversion imaging of the liver. Thirty-six patients had malignant disease (28
invasive parenchymal tumors and eight intraductal tumors), and 14 had benign
disease. The 36 malignancies included 29 cholangiocarcinomas, six invasive
gallbladder carcinomas, and one colon metastasis. Fourteen patients had benign
disease: benign strictures (n = 5), primary sclerosing cholangitis
(n = 5), chronic Mirizzi's syndrome (n = 1), varicosities of
the parabiliary venous plexus (n = 1), and inflammatory liver lesions
(n = 2). Sonographic findings in all 50 patients were correlated with
findings from other imaging modalities (n = 50) as well as surgical
specimens (n = 20), core biopsies (n = 3), and both clinical
and imaging follow-ups (n = 24).
RESULTS. Seventeen (61%) of the 28 invasive intraparenchymal
malignancies were visualized on routine sonograms, whereas all 28 (100%) were
visualized on enhanced sonograms (p < 0.01). In 15 (88%) of 17
patients in whom tumor was seen on routine sonograms, contrast-enhanced
sonography showed further mass extent, increased conspicuity, or satellite
nodules not visualized on the baseline image. All eight noninvasive
intraductal malignancies were correctly identified and staged on the routine
sonography. In one of these patients, hepatic invasion was prospectively
overcalled on the enhanced image. Of the 14 benign lesions, three had
inflammatory periductal abnormalities seen exclusively or to advantage on the
enhanced study. Correct prediction of resectability in the 16 patients with
malignant disease who underwent surgery improved from 11 (69%) of 16 on
unenhanced sonography to 15 (94%) of 16 on enhanced sonography (p =
0.13).
CONCLUSION. Detection and staging of malignant hilar obstructions
are improved by the use of Levovist in the postvascular phase of sonography
compared with routine sonography.
Introduction
Sonography remains the primary imaging modality for the initial assessment
of patients with biliary obstruction. As such, it often gives the first clues
to the presence of a malignant hilar obstruction. Worldwide, sonography
remains an important tool in the detection and staging of these lesions. The
literature suggests that sonography is quite accurate in local staging
compared with surgical or CT findings
[1,
2,
3]. However, the isoechoic
nature of the Klatskin's tumor and its propensity to grow in an infiltrative
periductal pattern make its detection and the determination of its extent
difficult. Often the location of the tumor is inferred from sonograms on the
basis of the level of ductal obstruction and irregularity of the walls of the
duct, whereas the actual borders of the lesion are not visualized
[4].
The contrast agent Levovist (SHU 508A; Schering, Berlin, Germany) has been
shown to persist in the normal hepatic parenchyma after a brief vascular
phase. This liver-specific postvascular phase of enhancement has been used for
improved visualization of hepatic malignancies. Several studies have shown
that use of Levovist results in increased conspicuity of metastases as well as
in the detection of more lesions compared with findings on unenhanced
sonography [5,
6,
7]. We hypothesized that
postvascular delayed sonograms obtained with Levovist would show increased
conspicuity of hilar cholangiocarcinoma, improving sonographic detection and
staging of this disease. In this preliminary study, we investigated the value
of Levovist-enhanced sonography of the liver as compared with that of
unenhanced sonography in patients presenting with hilar biliary
obstruction.
Subjects and Methods
Patients
Over a period of 20 months, consecutive patients presenting with hilar
biliary obstruction revealed on routine sonography with Doppler assessment
were prospectively recruited to undergo Levovist-enhanced postvascular
sonography of the liver. The study was approved by the ethics review board.
Signed informed consent was obtained from all patients. Fifty patients were
recruited, including 23 women and 27 men. The average age of the patients was
63.9 years (range, 36-82 years). All had clinical or laboratory evidence of
cholestasis.
Thirty-six of the 50 patients had a malignant hilar obstruction.
Twenty-eight of the 36 had an invasive intraparenchymal tumor. Eight of the 36
had an intraductal tumor (five affecting extrahepatic hilar ducts and three
involving the intrahepatic ducts only). Final diagnosis included 29 hilar
cholangiocarcinomas, six invasive carcinomas of the gallbladder, and one colon
metastasis. In 19 of the 36 patients with malignant disease, the diagnoses
were confirmed at surgical resection (n = 16) or biopsy (n =
3). For all patients who had a surgical resection, detailed pathologic
examination was performed on the surgical specimens, and the results were
compared with the sonographic findings. In 17 of the 36 patients, the clinical
and imaging features of overwhelming malignancy were such that palliative
therapy was administered without tissue biopsy or with inconclusive biopsy
results. Correlative imaging in the 36 patients with malignant disease
included CT scans (n = 21 patients), MR images (n = 16),
endoscopic retrograde cholangiopancreatograms (ERCP), or percutaneous
transhepatic cholangiograms (n = 7), and positron emission
tomographic scans (n = 1).
In 14 of the 50 patients, the cause of the hilar biliary obstruction was
related to benign disease: five benign strictures, five primary sclerosing
cholangitis, one case of chronic Mirizzi's syndrome, one case of varicosities
of the parabiliary venous plexus, and two inflammatory liver lesions. Both
inflammatory lesions were prospectively believed to represent malignant
lesions on all imaging modalities. All of the patients with sclerosing
cholangitis had clinical evidence of the disease. In all patients with benign
disease, the lack of progression of symptoms during follow-up (range of
follow-up periods, 6-16 months; mean, 12.8 months) and correlative imaging (MR
imaging, n = 8; ERCP or percutaneous transhepatic cholangiography,
n = 10; CT, n = 12); biopsy, (n = 1); and surgery,
(n = 4) were used to exclude malignancy and confirm sonographic
findings.
Sonographic Technique
All patients initially underwent a routine physician-performed sonographic
examination, which consisted of a thorough gray-scale evaluation of the liver,
bile ducts, and porta hepatis as well as color Doppler sonographic assessment
of the hepatic vasculature, with all findings being recorded. Independent of
this routine sonography, the patients underwent Levovist-enhanced sonography
performed on a scanner (model 5000; ATL Ultrasound, Bothell, WA) equipped with
pulse inversion grayscale imaging software. Two of the investigators performed
all examinations with a convex array probe (Apogee 800 C5-2; ATL Ultrasound)
and maximal allowed mechanical index (1-1.3). The contrast-enhanced
examination consisted of two unenhanced continuous sweeps (90 frames) in the
orthogonal transverse and sagittal planes to cover the entire liver and porta
hepatis, followed by identical sweeps performed 4 min after injection of the
contrast agent (300 mg/mL of Levovist in three boluses of 4.5 mL each).
Contrast-enhanced sweeps were performed in the sagittal and transverse planes,
as on the unenhanced study, with a third performed at the discretion of the
investigators to repeat the sweep providing the most information. All
unenhanced and contrast-enhanced sweeps were stored on our PACS (picture
archiving and communication system) as 90-frame cine loops.
Data Analysis
Without knowledge of the results from other imaging tests, the two authors
who performed the sonography prospectively interpreted all the images by
consensus. The initial routine sonogram was analyzed first, and the findings
were recorded. The contrast-enhanced sweeps were then carefully analyzed and
compared with the unenhanced sweeps and the initial sonographic findings.
Unenhanced and contrast-enhanced sweeps were placed side by side and analyzed
frame by frame to ensure direct comparison at exactly the same anatomic
location. To avoid overcalling normal nonenhancing structures in the liver as
evidence of disease, we used the unenhanced images as a reference for the
interpretation of the contrast-enhanced sonograms. If a focal abnormality was
detected on contrast-enhanced sonograms, the lesion was subjectively assessed
for size, conspicuity, and border definition in comparison with its depiction
on unenhanced sonograms. Because the postvascular enhancement with Levovist
affects only the liver, extrahepatic tumor extent and adenopathy were assessed
primarily with the baseline sonograms.
The determination of resectability was made by clinicians on the basis of
the results of all imaging examinations available to them. To determine the
usefulness of contrast-enhanced sonography as a tool to predict resectability
of hilar obstructive lesions if sonography alone had been used, we also
performed a separate analysis on all of the patients who had surgery
(n = 20). Sixteen of the patients had histologically proven
malignancies, and four had benign disease. Patients with benign entities that
were resected surgically included one patient with an inflammatory pseudotumor
of the liver, one patient with inflammatory periductal changes due to chronic
biliary obstruction, one patient with Mirizzi's syndrome, and one patient with
a benign stricture. In the surgical group, retrospective analysis of
resectability was determined by consensus of the three authors. The criteria
for resectability were based on criteria developed by Jarnagin et al.
[8] and are summarized in
Appendix 1. Statistical analysis was performed using the exact form of the
McNemar test.
Results
Patients with Malignant Tumors
Thirty-six patients were found to have malignant tumors, 28 had an invasive
tumor, and eight had only an intraductal tumor. We found 17 (61%) of 28
patients with intraparenchymal invasive tumor had a mass identified on the
unenhanced sonograms, whereas in 11 patients, the unenhanced sonograms did not
show a mass. The contrast-enhanced sonograms of all 28 patients with an
intraparenchymal invasive tumor showed a mass (Fig.
1A,
1B), a statistically
significant improvement in tumor detection (p < 0.01). Of the 17
masses seen on the unenhanced sonograms, 15 became more conspicuous after
enhancement and showed a wider extent of tumor, including satellite nodules
that were not seen on unenhanced sonography (Fig.
2A,
2B,
2C).
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Fig. 1A. —Malignant biliary obstruction in 68-year-old man with
invasive cholangiocarcinoma. Transverse unenhanced sonogram shows segmental
dilated ducts in right lobe that terminate blindly in region of porta hepatis.
No mass is visualized.
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Fig. 1B. —Malignant biliary obstruction in 68-year-old man with
invasive cholangiocarcinoma. Transverse postvascular contrast-enhanced
sonogram shows large invasive tumor with intraductal and periductal
extension.
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Fig. 2A. —Malignant hilar obstruction from cholangiocarcinoma with
metastatic liver nodules in 77-year-old man. Transverse unenhanced sonogram
shows mass in left lobe and dilated ducts (arrowheads) in right lobe
of liver.
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Fig. 2B. —Malignant hilar obstruction from cholangiocarcinoma with
metastatic liver nodules in 77-year-old man. Transverse contrast-enhanced
sonogram clearly shows larger mass with increased conspicuity and better
defined borders. Also visible is small isolated metastasis in liver
(arrow) that was seen only on enhanced imaging.
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Of the eight patients with only an intraductal tumor, an intraductal
irregularity (n = 2) or extrahepatic tumor (n = 5) was seen
on the unenhanced sonogram with no evidence of intraparenchymal invasion on
contrast-enhanced sonograms (Figs.
3A,
3B,
3C and
4A,
4B,
4C). In one patient,
unenhanced sonography was correctly interpreted as showing an intraductal
tumor, whereas contrast-enhanced sonography was falsely interpreted as
revealing an intraductal tumor with parenchymal invasion. The surgical
specimen showed the intraductal tumor only.
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Fig. 3A. —Malignant hilar obstruction from invasive gallbladder
carcinoma with extensive intraductal tumor extension in 83-year-old woman.
Transverse unenhanced sonogram shows dilated intrahepatic biliary ducts and
visible intraductal tumor (arrowheads).
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Fig. 3B. —Malignant hilar obstruction from invasive gallbladder
carcinoma with extensive intraductal tumor extension in 83-year-old woman.
Transverse contrast-enhanced sonogram improves conspicuity of duct walls and
intraductal tumor (arrowheads). No invasive tumor is seen at this
level.
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Fig. 3C. —Malignant hilar obstruction from invasive gallbladder
carcinoma with extensive intraductal tumor extension in 83-year-old woman. CT
scan obtained at same level does not depict intraductal tumor. Invasive
obstructing mass (not shown) at porta hepatis was seen on another CT scan and
on postvascular phase contrast-enhanced sonogram.
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Fig. 4A. —Malignant hilar obstruction from cholangiocarcinoma in
42-year-old man with large intraductal tumor. Transverse unenhanced sonogram
of left lobe of liver shows poorly defined mass (arrowheads).
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Fig. 4B. —Malignant hilar obstruction from cholangiocarcinoma in
42-year-old man with large intraductal tumor. Transverse contrast-enhanced
sonogram shows abnormality to be tumor-filled left hepatic duct
(arrowheads). No parenchymal invasion is seen.
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When a tumor was identified on unenhanced sonography, it appeared as a
hypoechoic mass, with the exception of an intraductal polypoid lesion and a
colon metastasis, both of which were echogenic. On contrast-enhanced
sonography, all masses appeared hypoechoic compared with the enhanced liver
parenchyma. None of the masses showed significant vascularity on the color
Doppler sonographic assessment.
Patients with Benign Disease
Fourteen patients had benign lesions. Five patients had primary sclerosing
cholangitis, four of whom exhibited ductal irregularity and wall thickening on
both unenhanced and contrast-enhanced sonography with no evidence of an
intraparenchymal mass. In the fifth patient, extensive periductal tissue was
identified on the contrast-enhanced sonograms that had not been identified on
the unenhanced images (Fig.
5A,
5B,
5C). These findings were
exactly as those seen on the patient's CT scan, and on both modalities the
findings were correctly predicted to represent benign disease.
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Fig. 5A. —Benign biliary obstruction due to primary sclerosing
cholangitis in 42-year-old woman with periductal thickening. Transverse
unenhanced sonogram obtained through porta hepatis reveals periportal region
with vague slightly hypoechoic areas (arrowheads).
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Fig. 5B. —Benign biliary obstruction due to primary sclerosing
cholangitis in 42-year-old woman with periductal thickening. Transverse
contrast-enhanced sonogram shows extensive periductal soft-tissue thickening
(arrowheads) around central biliary tree.
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Fig. 5C. —Benign biliary obstruction due to primary sclerosing
cholangitis in 42-year-old woman with periductal thickening. Confirmatory
contrast-enhanced CT scan shows regions (arrowheads) as
hypoattenuating relative to enhancing liver.
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In seven of the nine patients with other types of benign disease, no
evidence of an invasive intraparenchymal mass was seen on either unenhanced or
contrast-enhanced sonography. In one patient who had undergone a prior liver
resection for cholangiocarcinoma, extensive periductal masses surrounding a
dilated segmental duct were identified on contrast-enhanced sonography and MR
imaging; the masses were incorrectly interpreted as recurrent
cholangiocarcinoma on both modalities (Fig.
6A,
6B,
6C). The final histologic
evaluation showed inflammatory and fibrotic tissue surrounding an anomalous,
surgically obstructed bile duct. In another patient, all imaging modalities
(MR imaging, CT, and unenhanced and contrast-enhanced sonography) showed
multifocal hilar masses believed to represent a Klatskin's tumor. At
pathology, surgical specimens showed extensive peribiliary inflammation of
unknown origin without evidence of malignancy.
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Fig. 6A. —Benign inflammatory masses mimicking cholangiocarcinoma on
contrast-enhanced sonography and MR imaging in 63-year-old man 6 years after
left liver resection for cholangiocarcinoma. Transverse sonogram shows dilated
segmental bile duct (arrow) at resection margin in liver ventral
relative to right portal vein.
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Fig. 6B. —Benign inflammatory masses mimicking cholangiocarcinoma on
contrast-enhanced sonography and MR imaging in 63-year-old man 6 years after
left liver resection for cholangiocarcinoma. Transverse postvascular
contrast-enhanced sonogram obtained in same plane as A shows multiple
nonenhancing nodules (arrowhead) in periductal region
(arrow).
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Fig. 6C. —Benign inflammatory masses mimicking cholangiocarcinoma on
contrast-enhanced sonography and MR imaging in 63-year-old man 6 years after
left liver resection for cholangiocarcinoma. Confirmatory gadolinium-enhanced
T1-weighted MR image shows same dilated segmental bile duct (arrow)
surrounded by enhancing soft-tissue nodules (arrowhead). Both MR
image and sonogram were interpreted as showing recurrent
cholangiocarcinoma.
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Analysis of Patients Who Underwent Surgery
Twenty patients of the 50 in our study underwent surgery, 16 patients with
malignancies and four with benign conditions. In patients with malignant
disease, resectability was correctly predicted in 11 (69%) of 16 using
unenhanced sonography and in 15 (94%) of 16 on Levovist-enhanced sonography.
The improvement in prediction of resectability was not statistically
significant (p = 0.13), likely due to the small number of patients in
this subgroup; however, there is a clear trend of improvement when
contrast-enhanced sonography was used.
Successful surgical resection was correctly predicted in all four patients
with benign disease on both unenhanced and contrast-enhanced sonography. In
the two patients with benign inflammatory liver masses associated with hilar
biliary obstruction, the location and extent of disease were correctly
identified on postvascular phase sonography. In these two patients, findings
on all imaging modalities led to incorrect preoperative predictions of
malignancy.
Discussion
Cholangiocarcinoma remains a diagnostic challenge using any imaging
modality. Although a large unresectable mass is often easily detectable, the
infiltrative growth pattern, desmoplastic nature, and the propensity of
cholangiocarcinoma to grow axially along segmental ducts make this type of
lesion hard to detect. Sonography is usually the first cross-sectional
modality used in the assessment of patients with cholestatic symptoms. In the
imaging literature, there is general agreement that sonography is well suited
to depicting the level of obstruction but controversy over its sensitivity for
detection of the actual mass. Studies have reported rates of sonographic
detection of masses ranging from 21% to 87%, with more recent studies
reporting higher rates [1,
2,
9]. Our own experience suggests
that an infiltrative tumor is poorly depicted on sonography and that the
location of the tumor must be inferred from secondary findings, such as ductal
irregularity, ductal obstruction, and vascular compromise, revealed on
unenhanced gray-scale and Doppler sonography
[4] (Fig.
1A,
1B). We believe that polypoid
intraductal or large lesions are often well depicted on sonography.
The liver-specific, postvascular phase of contrast enhancement of liver
with Levovist has been well described in the literature
[5,
6,
7,
10]. The microbubbles are
selectively trapped in the hepatic parenchyma a few minutes after
intravascular injection of the contrast agent. A high-mechanical-index sweep
through the liver produces bright transient enhancement of the liver as the
accumulated microbubbles are destroyed. The marked increase in the
echogenicity of the liver parenchyma greatly improves the contrast between
liver and nonhepatocytic components such as portal triads and liver
masses.
Several studies have documented improved detection of metastases and
hepatocellular carcinoma [5,
6,
7]. To our knowledge,
cholangiocarcinoma has not routinely been evaluated with Levovist-enhanced
sonography, although in a series of 46 patients with liver masses studied by
Bertolotto et al. [10], two
cases of peripheral cholangiocarcinoma were included.
Most (36/50) of our patients had a malignancy, a reflection of the surgical
referral pattern in our institution. Levovist-enhanced sonography successfully
depicted the obstructing lesion in all 36 patients with malignant hilar
obstruction. In 11 (39%) of the 28 patients with an invasive intraparenchymal
tumor, the mass was seen only on the contrast-enhanced examinations, a
statistically significant improvement. In 15 (88%) of the 17 patients with
invasive tumor that was seen on unenhanced sonography, further extension of
the mass and increased conspicuity were noted on the enhanced sonography. The
results of our study show that postvascular phase Levovist-enhanced sonography
greatly improved the detection and determination of the extent of hilar
malignant disease, which led to improved staging and resultant change in
management in some patients. Failure of contrast-enhanced sonography to reveal
a mass in patients with benign pathology increased our confidence level in
recommending conservative management.
The main and the distal right and left hepatic ducts are extrahepatic, but
their branches extend immediately into the liver. Malignant hilar
cholangiocarcinoma has a propensity to grow axially along and into the ducts
and invade the liver parenchyma. It is this invasive component that Levovist
enhancement excellently depicts, particularly as the periductal supportive
tissue becomes thinner with higher order branching. Frequently, on enhanced
sonography, tumor resembling a grapelike cluster can be seen following the
ducts into the liver. These small invasive foci are often not seen on
unenhanced sonography due to the isoechoic nature of the lesions. Sonography
has excellent spatial resolution, and our results suggest that Levovist
enhancement improves the contrast resolution of the modality and therefore its
sensitivity for tumor detection. We believe that Levovist-enhanced sonography
probably offers no significant improvement in specificity over unenhanced
sonography, because all nonhepatocytic tissues are nonenhancing, including
both tumor and inflammatory or fibrotic foci (Figs.
5A,
5B,
5C and
6A,
6B,
6C).
Our major objective in this preliminary study was not to test the
diagnostic performance of Levovist-enhanced sonography against other imaging
tests but rather to determine whether the technique had the potential to
improve the performance of sonography used in the assessment of hilar biliary
obstruction. Our protocol did not include correlative imaging, which was
performed at the discretion of the referring clinician. In addition, only 20
patients underwent the gold standard of surgery. For both of these reasons, we
could not compare the performance of contrast-enhanced sonography with that of
CT or MR imaging. We did, however, confirm the results with all available
clinical and imaging records and with follow-up examinations. Our analysis
showed that two patients predicted to have unresectable disease on the basis
of postvascular phase Levovist-enhanced sonography were found to have
unresectable disease; surgery had been performed because CT findings suggested
resectable disease.
Important principles for the accurate interpretation of contrast-enhanced
sonograms are well exemplified by the two false-positive results in our study.
Extensive benign fibrotic and inflammatory nodules surrounding a dilated
segmental duct were mistaken for tumor on both sonography and MR imaging in a
man who had undergone liver resection 6 years earlier (Fig.
6A,
6B,
6C). In another patient,
multifocal periductal masses seen on all imaging modalities were incorrectly
interpreted as representing cholangiocarcinoma. At pathology, a surgical
specimen revealed benign peribiliary inflammatory masses. These cases taught
us the importance of recognizing that only hepatocyte-containing tissue
enhances; therefore, all other types of tissue appear hypoechoic compared with
the enhancing liver parenchyma. These tissues include tumor, fibrous and
inflammatory tissue, normal periductal connective tissue of the portal triads,
and (occasionally) tissue of the portal vein and hepatic artery branches.
The lack of enhancement of normal connective tissue also led to overcalling
the extent of tumor seen in a third patient on contrast-enhanced sonography.
An intraductal tumor adjacent to the ascending left portal venous branch was
interpreted as showing parenchymal invasion; however, the finding actually
represented normal connective tissue in the portal triad. Direct analysis with
the unenhanced scan made this obvious in retrospect. The error occurred early
in our study (our seventh patient). Our result was concordant with a CT scan,
and neither finding altered the tumor stage or treatment. The case of this
patient reinforced our belief in the necessity of careful side-by-side
analysis of unenhanced and contrast-enhanced cine loops to correctly estimate
tumor extent and to correctly identify the normal liver vasculature and
supporting stroma on the enhanced sonograms. We found that orthogonal sweeps
were essential to confirming or discounting questionable lesions seen in one
plane.
We acknowledge that there is a significant learning curve for the
successful performance of Levovist-enhanced postvascular phase sonography. The
person performing the examination must be able to cover, in a single sweep, as
much of the liver as the direction of the sweep allows. Several practice
sweeps are required to find the optimal patient and transducer positions, as
well as the best sweep direction and speed. The practice sweeps also allow the
patient to become familiar with the technique and with the requirement for a
long suspended inspiration, which must be maintained for the entire sweep.
Furthermore, to prevent bubble destruction, the sonographic mechanism must be
frozen before the initiation of the sweep. The mechanical index must be
maximal to produce good bubble destruction during the sweep, and the gain must
be lowered to avoid a very bright and difficult-to-interpret image. The focal
zone is best set at the level of the porta hepatis to clearly depict disease
centered at this level of the liver. We did not measure the duration of the
contrast-enhanced examination because study times became progressively shorter
with increased proficiency. We believe that the contrast-enhanced study adds
30-45 min to the routine sonographic examination, including the interpretation
of the findings, which can be performed after the patient has left the
department.
The fact that both the unenhanced and contrast-enhanced sonograms were
interpreted by the same authors at the same sitting may have introduced bias
in the interpretations and is a limitation of the study methodology. However,
because there was an obvious advantage in using the contrast-enhanced
sonography for most patients, the additional information was shared with the
clinicians, making temporally separate analyses impossible.
Our study has shown that following an unenhanced sonographic examination
with a Levovist-enhanced sonographic examination significantly improved both
the intrahepatic detection and staging of malignant biliary obstruction
compared with using an unenhanced examination alone. Direct identification of
cholangiocarcinoma augments information that previously had to be inferred
from indirect evidence such as segmental intraductal dilatation. In our
institution, our clinicians have adopted postvascular phase Levovist-enhanced
sonography as a standard method of evaluating hilar obstructions. We are
currently engaged in a prospective study comparing the performance of
unenhanced and Levovist-enhanced sonography with the performances of MR
imaging and MR cholangiography.
Although Levovist is not approved for medical imaging in the United States,
phase III trials of several second-generation contrast agents are now being
conducted. Some of these contrast agents offer the same postvascular
enhancement of normal liver tissue that Levovist provides.
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Abstract
Introduction
