Diagnostic Ultrasound - Abdomen and Pelvis

Pyogenic Hepatic Abscess
Diagnoses: Liver
TERMINOLOGY
• Localized collection of pus in liver due to bacterial
infectious process with destruction of hepatic parenchyma
and stroma
IMAGING
• Cluster sign: Cluster of small pyogenic abscesses that
coalesce into single large cavity
• Ultrasound:Early lesions tend to be echogenic and poorly
demarcated, evolve into well-demarcated anechoic lesions
• CECT: Double target sign
• May see central gas or fluid level
TOP DIFFERENTIAL DIAGNOSES
• Metastasis (post-treatment)
• Cholangiocarcinoma (peripheral mass-forming)
• Biliary cystadenocarcinoma
• Hepatocellular carcinoma (hypovascular)
• Amebic abscess
KEY FACTS
• Hemangioma (small)
• Hemorrhagic simple cyst
• Hydatid cyst (echinococcal cyst)
• Hepatic infarction in liver transplantation
PATHOLOGY
• Development via 5 major routes: Portal vein, biliary tract,
hepatic artery, direct extension, trauma
• Common organisms: Escherichia coli, Klebsiella pneumoniae
(adult), Staphylococcus aureus (children)
CLINICAL ISSUES
• Accounts for 88% of all liver abscesses
• Typical presentation: Middle-aged/elderly patient with
history of fever, RUQ pain, tender hepatomegaly,
leukocytosis
DIAGNOSTIC CHECKLIST
• Rule out amebic/fungal liver abscesses, cystic/hypovascular
tumors
(Left) Transverse graphic
shows a cluster of multiple
variable-sized pus collections
in the right lobe of the liver ſt
coalescing to form a large
abscess cavity . (Right)
Oblique transabdominal color
Doppler ultrasound shows a
cluster of coalescing abscesses
ſt in the right lobe of liver,
representing a pyogenic
hepatic abscess. The abscess
has irregular walls, and
contains low level internal
echoes st. Adjacent hepatic
parenchyma is edematous and
hypervascular .
(Left) Oblique transabdominal
grayscale ultrasound shows an
irregular-shaped hypoechoic
pyogenic abscess ſt in the
right lobe of the liver. Several
internal septations are
seen, as well as peripheral
echogenic components of the
abscess st. (Right) Oblique
transabdominal color Doppler
ultrasound performed in the
same patient shows no color
flow within the abscess cavity
ſt. Note irregular internal
echogenic debris st within the
abscess cavity.
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