Diagnostic Ultrasound - Abdomen and Pelvis

Amebic Hepatic Abscess
Diagnoses: Liver
TERMINOLOGY
• Localized pus collection in liver due to Entamoeba
histolytica with destruction of hepatic parenchyma
IMAGING
• General feature
○ Most often solitary (85%), peripherally located
• Ultrasound
○ Sharply demarcated, round or ovoid mass
○ Hypoechoic with low-level internal echoes
○ May see internal septa or wall nodularity
○ May see posterior acoustic enhancement
• CECT
○ Typically hypoattenuating unilocular lesion
○ Peripheral rim or capsule enhancement
○ May see hypodense halo due to edema
TOP DIFFERENTIAL DIAGNOSES
• Hepatic metastasis (post-treatment, cystic, or necrotic)
KEY FACTS
• Hepatic pyogenic abscess
• Hepatic hydatid cyst
• Biliary cystadenoma/cystadenocarcinoma
• Infarcted liver after transplantation
PATHOLOGY
• Entamoeba histolytica
• Primary source of infection: Human carriers passing amebic
cysts into stool
CLINICAL ISSUES
• RUQ pain, tender hepatomegaly, diarrhea with mucus
• Indirect hemagglutination positive in 90% of cases
DIAGNOSTIC CHECKLIST
• Rule out pyogenic or fungal abscess, cystic lesions
• Check for history of transplantation, ablation, or
chemotherapy for liver tumor or metastasis, which may
simulate amebic abscess on imaging
(Left) Graphic illustration
demonstrates a unilocular
encapsulated amebic abscess
within the liver. Note the
surrounding rim of edema ſt
and central anchovy paste
consistency of contents .
(Right) Sagittal gray scale
ultrasound of the liver shows a
large, well-demarcated and
encapsulated hypoechoic
amebic abscess ſt. The
contents are heterogeneous
due to floating debris st. Also
note the mild posterior
acoustic enhancement .
(Left) Color Doppler
ultrasound in the same patient
shows no detectable internal
vascularity within the lesion
ſt. (Right) Coronal contrastenhanced
CT in same patient
shows a large unilocular
amebic abscess in the right
lobe of liver. The abscess is
well defined with an
enhancing capsule st and
hypodense halo of edema .
Note the abutment with liver
capsule .
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