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AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY |
1 Division of Abdominal Imaging and Interventional Radiology, Department of
Radiology, Massachusetts General Hospital and Harvard Medical School, Boston,
MA.
2 Department of Radiology, Children's Mercy Hospitals and Clinics and the
University of Missouri-Kansas City, Kansas City, MO.
3 Department of Diagnostic Radiology, Mayo Clinic, 13400 E Shea Blvd.,
Scottsdale, AZ.
Received January 28, 2008; accepted after revision January 29, 2008.
Address correspondence to A. C. Silva
(silva.alvin{at}mayo.edu).
Focal hepatic lesions are one of the diagnostic challenges in daily practice. This article focuses on the imaging features of focal hepatic lesions on different imaging modalities, including sonography, CT, and MRI.
Keywords: focal hepatic lesions • hemangiomatosis • hepatoblastoma • Staphylococcus aureus
INTRODUCTION
This self-assessment module on imaging of focal hepatic lesions has an educational component and a self-assessment component. The educational component consists of four required articles that the participant should read. An additional article is recommended. The self-assessment component consists of 12 multiple-choice questions with solutions. All of these materials are available on the ARRS Web site (www.arrs.org). To claim CME and SAM credit, each participant must enter his or her responses to the questions online.
EDUCATIONAL OBJECTIVES
By completing this educational activity, the participant will:
REQUIRED READING
RECOMMENDED READING
INSTRUCTIONS
| QUESTION 1 In children, which is the most common hepatic malignancy?
QUESTION 2 In children with pyogenic hepatic abscesses, which is the most common causative organism?
QUESTION 3
In infants with negative serum catecholamines and low
QUESTION 4 For a patient with hepatic hemangiomatosis documented by sonography, which would be the most appropriate additional imaging workup?
QUESTION 5 On sonography, which hepatic lesion is most typically hyperechoic?
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| QUESTION 6 In patients with a focal liver lesion, which MRI feature most strongly suggests inflammatory pseudotumor?
QUESTION 7 On MRI of the liver, all of the following lesions show delayed enhancement EXCEPT:
QUESTION 8 On MRI of the liver, which of the following is hyperintense on T2-weighted images?
QUESTION 9 In patients with chronic hepatitis C who develop primary hepatic lymphoma, which is the most common cellular type?
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| QUESTION 10 On contrast-enhanced CT of the liver, which of the following best describes "peripheral washout?"
QUESTION 11 On contrast-enhanced CT of the liver, which enhancement pattern indicates hemangioma?
QUESTION 12 In patients who have received chemotherapy for hepatic metastases, which imaging feature is most useful in distinguishing treated metastases from hemangioma?
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Solution to Question 1
Hepatoblastoma is the most common hepatic malignancy in children
[1,
2]. Option C is the best
response. Metastatic Wilms' tumor, angiosarcoma, hemangioendothelioma, and
metastatic neuroblastoma are less common then hepatoblastoma in this age
group. Options A, B, D, and E are not the best responses.
Solution to Question 2
Although all of the listed bacteria may be potential causes of pyogenic
liver abscesses, most literature recognizes Staphylococcus aureus as
the most common isolated organism
[3]. Option B is the best
response. Options A, C, D, and E are not the best responses.
Solution to Question 3
Because of the negative serum markers, hemangiomatosis would be the lesion
that would most commonly cause multiple hyperechoic hepatic lesions. Option
E is the best response. Although the described lesions can be seen with
metastatic neuroblastoma tumor, the negative serum markers allow confident
exclusion of this disease [4].
Option A is not the best response. Hepatoblastoma is excluded by a normal
-fetoprotein level. Option C is not the best response. The remaining
entities, angiosarcoma and leukemia, are much less common than multiple
hemangiomas in infants [5].
Options B and D are not the best responses.
Solution to Question 4
Hepatic hemangiomas typically undergo an initial proliferative phase
followed by regression and gradual involution
[6]. Therefore, no additional
imaging is required once the diagnosis is made
[7]. Option A is the best
response. Options B, C, D, and E are not the best responses because
additional imaging workup is not appropriate in this circumstance.
Solution to Question 5
Hepatocellular carcinoma and hepatocellular adenoma show variable
echogenicity on sonography [8].
Options A and B are not the best responses. Peripheral cholangiocarcinoma and
inflammatory pseudotumor usually appear as hypoechoic masses on sonography
[8,
9]. Options D and E are not the
best responses. Small hemangiomas most typically appear on sonography as
hyperechoic lesions. Option C is the best response.
Solution to Question 6
Inflammatory pseudotumors are composed of fibrous tissue associated with
mixed inflammatory cells and areas of necrosis. The marked fibrosis could be
responsible for the hypovascular appearance, with hypointensity on T1-weighted
images, mild hyperintensity on T2-weighted images, and late enhancement after
contrast material administration
[10]. Option A is the best
response. The other MRI features are not characteristic of inflammatory
pseudotumor. Options B, C, D, and E are not the best responses.
Solution to Question 7
Hemangiomas appear as typical enhancement characteristics of nodular
enhancement in the arterial phase images, followed by gradual centripetal
filling-in in the delayed phase images
[8]. Option A is not the best
response. Peripheral cholangiocarcinoma and inflammatory pseudotumor show a
hypovascular appearance with late enhancement after contrast material
administration [8,
10]. Options B and C are not
the best responses. Hepatocellular carcinomas typically show enhancement in
the arterial phase images and rapid contrast washout in the portal venous
phase images [8].
Hepatocellular carcinomas do not show delayed enhancement; therefore Option
D is the best response.
Solution to Question 8
Uncomplicated cyst fluid is hyperintense on T2-weighted MR images.
Option D is the best response. Hemosiderin deposition, calcification,
and fibrosis show hypointensity on T2-weighted MR images. Options A, B, and C
are not the best responses. Arteriovenous malformation with high flow also
appears hypointense on T2-weighted MR images due to flow void
[11]. Option E is not the best
response.
Solution to Question 9
Although both Hodgkin's and non-Hodgkin's lymphoma (NHL) can secondarily
involve the liver, most primary hepatic lymphomas are due to B-cell NHL. A
recent meta-analysis revealed an increased prevalence of hepatitis C virus
infection in patients with B-cell NHL, compared with both the general
population and patients with other types of hematologic malignancies
[12]. Option B is the best
response. Options A, C, D, and E are not the best responses.
Solution to Question 10
The "peripheral washout" sign has been described as occurring
only with malignant tumors
[13]. It is thought to occur
due to differences in regional vascularity of the tumor as it
enlarges—that is, as the tumor increases in size, the central region is
relatively ischemic or necrotic compared with the peripheral region. Thus, on
delayed contrast-enhanced images, the clearance of contrast material (washout)
from the peripheral regions is greater than that in the central regions. The
presumed more homogeneous vascularity is thought to explain why this finding
is not present in benign tumors. Option E is the best response. Options
A, B, C, and D are not the best responses.
Solution to Question 11
Three patterns of enhancement have been described for hemangiomas
[14]. The most common pattern
is early, peripheral, nodular, interrupted enhancement that progresses in a
centripetal fashion on later images, with contrast retention on delayed
images. The attenuation or signal should follow the blood pool. Large
hemangiomas typically appear similar on earlier images, but may have
persistent central hypoattentuation or hypodensity. Small hemangiomas can show
early, homogeneous hyperenhancement that persists on delayed images. Option
C is the best response. The patterns of enhancement described in the other
options are not described in hemangioma. Options A, B, D, and E are not the
best responses.
Solution to Question 12
Both hypervascular metastases and hemangiomas typically show T1-weighted
hypointensity and marked T2-weighted hyperintensity on unenhanced sequences.
In addition, because of the presumed antiangiogenesis effects of chemotherapy,
treated metastases can also show early nodular enhancement, as well as delayed
contrast retention due to enlarged extracellular spaces or decreased venous
drainage [15]. Thus, Options
A, B, C, and E are not distinguishing features and are not the best responses.
However, because hemangiomas classically exhibit interrupted peripheral
nodular enhancement, the finding of an intact, continuous, peripheral rim of
nodular enhancement in a patient undergoing chemotherapy should raise
suspicion for metastases. Option D is the best response.
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