Diagnostic ultrasound ( PDFDrive )

CHAPTER 4 The Liver 125
Advantages of ultrasound as a screening test for metastatic
liver disease include its relative accuracy, speed, lack of ionizing
radiation, and availability. Further, the multiplanar capability of
ultrasound allows for excellent segmental localization of masses,
with the ability to detect proximity to or involvement of the
vital vascular structures. Although isolated reports describe
detection of metastases on sonography in skilled hands as
competitive with CT and MRI, sonography is not uniformly
used as the irst-line investigative technique to search for
metastatic disease worldwide; CT has illed that role. Experience
suggests that ultrasound without microbubble contrast agents
does not compete with triphasic CT for metastasis detection. 136
Although greatly improved with the addition of contrast agents,
as described earlier, we doubt CEUS will ever be widely used in
routine clinical practice for the large numbers of patients who
have scans for metastatic disease. Nonetheless, on a case-bycase
basis, and as a problem-solving modality, CEUS may play a
contributory role in the evaluation of the patient with metastatic
liver disease.
On conventional gray-scale sonography, patients with
metastatic liver disease may present with a single liver lesion
(Fig. 4.59A), although more oten they present with multiple
focal liver masses. All metastatic lesions in a given liver may have
identical sonographic morphology; however, biopsy-conirmed
lesions of difering appearances may have the same underlying
histologic structure. Of importance, metastases may also be present
in a liver that already has an underlying difuse or focal abnormality,
most oten hemangioma. Metastatic involvement of the liver
may take on diferent forms, showing difuse liver involvement
and, in rare cases, geographic iniltration (Fig. 4.59C-F).
Knowledge of a prior or concomitant malignancy and features
of disseminated malignancy at sonography are helpful in correct
interpretation of sonographically detected liver masses. Although
no conirmatory features of metastatic disease are seen on
sonography, suggestive features include multiple solid lesions
of varying size and a hypoechoic halo surrounding a liver mass.
A halo around the periphery of a liver mass on sonography is
an ominous sign strongly associated with malignancy, particularly
metastatic disease but also HCC.
In our investigation of 214 consecutive patients with focal
liver lesions, 66 had lesions that showed a hypoechoic halo; 13
had HCCs (Fig. 4.60A and B); 43 had metastases (Fig. 4.60C-F);
four had FNH; and two had adenomas (see Fig. 4.51). Four
lesions were unconirmed. In 1992, Wernecke et al. 195 described
the importance of the hypoechoic halo in the diferentiation of
malignant from benign focal hepatic lesions. Its identiication
has a positive and negative predictive value of 86% and 88%,
respectively. herefore we conclude that although not absolutely
indicative of malignancy, a halo is seen with lesions that require
further investigation and conirmation of their nature, regardless
of the patient’s presentation or status. Radiologic-histologic
correlation of a hypoechoic halo surrounding a liver mass has
revealed that, in the majority of cases, the hypoechoic rim corresponds
to normal liver parenchyma, which is compressed by
the rapidly expanding tumor. Less frequently, the hypoechoic
rim represents proliferating malignant cells, tumor ibrosis or
vascularization, or a ibrotic rim. 196-198
he sonographic appearance of metastatic liver disease has
been described as echogenic, hypoechoic, target, calciied, cystic,
and difuse. Although the ultrasound appearance is not speciic
for determining the origin of the metastasis, certain generalities
apply (Fig. 4.61).
Echogenic metastases tend to arise from a gastrointestinal
origin or from HCC (Fig. 4.61I). he more vascular the tumor
is, the more likely it is that the lesion is echogenic. 180,199 herefore
metastases from renal cell carcinoma, neuroendocrine tumors,
carcinoid, choriocarcinoma, and islet cell carcinoma also tend
to be hyperechoic. It is this particular group of tumors that may
mimic a hemangioma on sonography.
Hypoechoic metastases are generally hypovascular and may
be monocellular or hypercellular without interstitial stroma.
Hypoechoic lesions represent the typical pattern seen in untreated
metastatic breast or lung cancer (Figs. 4.60 and 4.61), as well as
gastric, pancreatic, and esophageal tumors. Lymphomatous
involvement of the liver may also manifest as hypoechoic masses
(Fig. 4.62). he uniform cellularity of lymphoma without signiicant
background stroma is thought to be related to its
hypoechoic appearance on sonography. Although at autopsy the
liver is oten a secondary site of involvement by Hodgkin and
non-Hodgkin lymphoma, the disease tends to be difusely
iniltrative and undetected by sonography and CT. 200 he pattern
of multiple hypoechoic hepatic masses is more typical of primary
non-Hodgkin lymphoma of the liver or lymphoma associated
with AIDS. 200,201 he lymphomatous masses may appear anechoic
and septated, mimicking hepatic abscesses.
he bull’s-eye or target pattern is characterized by a peripheral
hypoechoic zone (see Fig. 4.60). he appearance is nonspeciic
and common, although it is frequently identiied in metastases
from bronchogenic carcinoma. 202
Calciied metastases are distinctive by virtue of their marked
echogenicity and distal acoustic shadowing (Fig. 4.61B). Mucinous
adenocarcinoma of the colon is most frequently associated with
calciied metastases. Calcium may appear as large, echogenic,
and shadowing foci or, more oten, shows innumerable tiny
punctate echogenicities without clear shadowing. Other primary
malignancies that give rise to calciied metastases are endocrine
pancreatic tumors, leiomyosarcoma, adenocarcinoma of the
stomach, neuroblastoma, osteogenic sarcoma, chondrosarcoma,
and ovarian cystadenocarcinoma and teratocarcinoma. 203
Cystic metastases are uncommon and generally exhibit features
that distinguish them from the ubiquitous benign hepatic cyst,
including mural nodules, thick walls, luid-luid levels, and internal
septations. 204,205 Primary neoplasms with a cystic component,
such as cystadenocarcinoma of the ovary and pancreas and
mucinous carcinoma of the colon, may produce cystic secondary
lesions, although infrequently. More oten, cystic neoplasms result
from extensive necrosis, seen most oten in metastatic sarcomas,
which typically have low-level echoes and a thickened, shaggy
wall (Fig. 4.61H). Metastatic neuroendocrine and carcinoid
tumors are typically highly echogenic and oten show secondary
cystic change (Fig. 4.61I). Large colorectal metastases may also
rarely be necrotic, producing a predominantly cystic liver mass.
Difuse disorganization of the hepatic parenchyma relects
iniltrative metastatic disease and is the most diicult to