Diagnostic Ultrasound - Abdomen and Pelvis

Hypoechoic Liver Mass
876
Differential Diagnoses: Liver
DIFFERENTIAL DIAGNOSIS
Common
• Complicated Benign Hepatic Cyst
• Hepatic Metastases
• Infection
○ Pyogenic Hepatic Abscess
○ Amebic Hepatic Abscess
○ Fungal Hepatic Abscess
• Focal Fatty Sparing
• Hepatocellular Carcinoma
• Infected Biloma
Less Common
• Hepatic Lymphoma
• Hepatic Adenoma
• Focal Nodular Hyperplasia
• Atypical Hemangioma
• Hepatic Hematoma
• Abnormal Bile Ducts
• Abnormal Vessels
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Lesions of lower echogenicity than liver parenchyma
(compared to purely anechoic lesions)
○ With some low-level internal echogenicity
○ Solid lesion vs. complex cystic lesion
Helpful Clues for Common Diagnoses
• Complicated Benign Hepatic Cyst
○ Superimposed hemorrhage or infection in hepatic cyst
○ Septation/thickened wall ± mural calcification
○ Posterior acoustic enhancement
○ Solid appearance
– If internal debris (clots or fibrin strands) dispersed
within cyst
○ Fluid-debris level
– If debris settles under influence of gravity
○ No mural nodule
○ Color Doppler
– Absence of internal or mural vascularity
– Adjacent vessels distorted by large cyst
• Hepatic Metastases
○ Hypoechoic metastases tend to be numerous and small
– Larger lesions tend to have heterogeneous
echogenicity
○ May have irregular or ill-defined borders
○ Hypoechogenicity
– May reflect poor cellular differentiation and active
growth
○ Suggest hypovascular and hypercellular tumor origin
– Lung, breast, lymphoma
○ No posterior acoustic enhancement
○ Causes architectural distortion
– If large or numerous
○ Color Doppler may show no vascularity
– Most are hypovascular
○ Difficult to differentiate from lymphoma without history
of known primary lesion
• Pyogenic Hepatic Abscess
○ Cystic mass with irregular border and debris
○ Posterior acoustic enhancement
○ Multiple thick or thin septations
○ Mural nodularity & vascularity
○ Adjacent parenchyma may be coarse & hypoechoic due
to inflammation
○ "Cluster" sign: Coalescence of group of abscesses
○ May contain gas within abscess
– Reverberation artifact or air-fluid level
○ Changes to anechoic when center becomes necrotic as
center enlarges
○ Periportal distribution suggests dissemination along
biliary tree
○ Random distribution suggests hematogenous spread
• Amebic Hepatic Abscess
○ Abuts liver capsule, under diaphragm
○ More likely to be round or oval-shaped than pyogenic
abscess
○ Hypoechoic with fine internal echoes
– More common in amebic than pyogenic abscess
○ Internal septa may be present
○ Posterior acoustic enhancement
○ No vascularity seen in wall or septa of abscess
○ Subdiaphragmatic rupture in presence of adjacent
hepatic abscess
– Suggests amebic nature of abscess
• Focal Fatty Sparing
○ Geographic hypoechoic area within echogenic liver
○ Due to direct drainage of hepatic flow into systemic
circulation
○ Typical locations
– Gallbladder fossa
□ Drained by cystic vein
– Inferior aspect of segment 4b
□ Drained by aberrant gastric vein
– Anterior to bifurcation of portal vein
□ Drained by aberrant gastric vein
– Around hepatic veins
○ No architectural distortion
– Vessels course through mass undistorted
– No mass effect
○ Does not cross segments
• Hepatocellular Carcinoma (HCC)
○ Hypoechoic: Most common US appearance of HCC
– Solid tumor
– May be surrounded by thin, hypoechoic halo (capsule)
○ Background cirrhotic liver
○ Associated signs of portal hypertension
– Ascites, splenomegaly, portosystemic collaterals
○ Color Doppler
– Irregular hypervascularity
– Portal vein thrombus with arterial neovascularity
• Infected Biloma
○ Fluid collection within liver, close to biliary tree, or in
gallbladder fossa
○ Debris or septa suggest infected biloma
○ Color Doppler
– No vascularity within lesion