Liver Evaluation

• Liver Evaluation

Patient Preparation

• Patients should have nothing by mouth (NBM) for 6 hours before the evaluation.
• Only clear fluids are allowed.
• Patients should be positioned supine for the procedure.

Transducer Selection

• A curvilinear probe with a frequency of 1-5 MHz is used in liver evaluations.
• This is a low frequency transducer.

Liver Size

• Maximum liver dimension/span is less than 15cm.
• Cranio-caudal dimension is typically between 10cm and 12.5cm.
• Enlargement of the liver could be caused by Hepatitis, Alcoholic liver disease, Nonalcoholic liver disease/ fatty liver, or Tumors

Texture

• Liver texture refers to the characteristic pattern or structure of a tissue layer observed in ultrasound.

Echogenicity

• Echogenicity is the ability of a tissue to send back an ultrasound signal.
• Tissue with higher echogenicity is hyperechogenic, appearing bright on the image.
• Tissue with lower echogenicity is hypoechogenic, appearing less bright.
• Structures with no echogenicity are anechoic, appearing dark on the image.

Indications for Liver Evaluation

• Right Upper Quadrant (RUQ) pain.
• Enlarged liver.
• Jaundice.
• Abdominal trauma.
• Ascites.
• Suspicion of a liver mass or abscess.
• Deranged liver function.

Liver Cirrhosis

• Features of liver cirrhosis include:
• Coarse liver echotexture.
• Irregular liver surface.
• Enlargement of the caudate lobe.

Hepatitis

• Hepatitis can present with the following ultrasound characteristics:
• Diffusely hypoechoic appearance.
• Accentuated portal tracts in contrast.
• "Starry night" or "starry sky" appearance.

Fatty Liver

• Fatty liver can present with the following ultrasound characteristics:
• Increased echogenicity.
• Decreased definition of portal vein walls.
• Posterior sound attenuation.

Metastasis

• Metastasis in the liver:
• Hyperechoic masses.
• Bull's eye or target lesions.
• Cystic masses.
• Diffuse pattern.

Evaluation of Abnormalities

• Echogenicity can be hyper, hypo, or anechoic.
• Artifacts to look for include posterior shadowing, posterior enhancement, and comet-tail artifacts.
• Shapes can be round, irregular, or lobulated.
• Margins can be sharp or ill-defined.
• Size should be measured in three dimensions.
• Internal structure: can have a hypoechoic rim, and be heterogeneous or homogenous, solid, or cystic.
• Number: solitary or multiple.
• Location: specified by segment.
• Vascularity: peripheral or penetrating.

Simple Liver Cysts

• Anechoic.
• A smooth wall margin.
• Posterior enhancement.

Complex Liver Cysts

• Anechoic.
• May contain septations or internal echoes.
• Posterior enhancement.

Enhancement vs. Shadowing

• Attenuation assumes uniformity, with baseline Time Gain Compensation (TGC) amplifying echoes from deeper tissues.
• Less attenuating tissue results in a brighter beam distally due to overcompensation from TGC.
• More attenuating tissue results in a less intense beam distally, making the tissue appear darker.

Focal Fatty Sparing

• Localized absence of increased intracellular fat.

Focal Fatty Infiltration/ Hepatic Steatosis

• Small area of liver steatosis.

Cavernous Haemangioma

• Homogenous hyperechoic mass (commonly).
• The mass has a well-defined margin that is round.
• Peripheral feeding vessels may be seen.
• Possible complex echo pattern from hemorrhage or necrosis.

Mass (Adenoma/ Focal Nodular Hyperplasia/ HCC)

• The mass can be hypoechoic, hyperechoic, or heterogeneous.
• A hypoechoic halo may be visible.
• Penetrating vessels may be seen.
• Possible echogenic focus or microcalcification.

Portal Vein Evaluation

• AP diameter = 1.3cm.
• Diameter should increase by 20-30% with food intake and inspiration.
• Flow direction is towards the liver.

PV Thrombosis

• Acute thrombosis is hypoechoic.
• Chronic thrombosis is echogenic.
• Color flow can demonstrate absent or partial flow.
• The PV diameter can increase.

Portal Hypertension

• Main portal vein measures >13mm.
• Hepatomegaly.
• Splenomegaly.
• Venous collateral formation.