Liver ultrasound

Last revised by Henry Knipe on 5 Jun 2023

Liver ultrasound is a valuable diagnostic tool for assessing liver anatomy, size, and pathology. It is a non-invasive, painless, and relatively quick procedure that does not involve exposure to ionizing radiation.

Liver ultrasound is commonly utilized in the evaluation of various hepatic conditions. The most frequent indications include 1,2:

  • screening for hepatic disease in at-risk populations (e.g. hepatocellular cancer screening in cirrhotic patients)

  • investigation of abnormal liver function tests

  • evaluation of focal liver lesions detected on other imaging modalities

  • assessment of liver size in patients with suspected hepatomegaly

  • monitoring chronic liver disease

  • assessment of portal venous system and bile ducts in patients with possible obstruction

  • guiding biopsies or therapeutic interventions

Before conducting a liver ultrasound examination, the patient should ideally fast for at least 6 hours to minimize bowel gas interference. The examination consists of grayscale B-mode imaging complemented by Doppler studies if necessary. To optimize image quality and facilitate accurate assessment of the entire liver, use proper gain settings and probe manipulation is crucial.

Anatomic structures that are expected to be visualized during routine liver ultrasound include the right/left lobes of the liver, caudate lobe, intrahepatic blood vessels (portal, hepatic veins), gallbladder, and extrahepatic bile ducts.

Common findings of a normal ultrasound examination should include 2,3:

  • homogeneous parenchymal echogenicity

  • smooth capsule with a regular contour

  • normal size of liver lobes: right lobe measuring 13-15 cm in craniocaudal dimension, and left lobe measuring <7 cm in width

  • patent intrahepatic vasculature with no evidence of thrombosis or dilatation

  • gallbladder free of stones and normal wall thickness (<3 mm)

  • common bile duct measuring <6 mm in diameter

Some common pathologies and abnormal findings that could be detected during liver ultrasound examination are:

  • focal liver lesions, e.g. cysts, hemangiomas, metastases, hepatocellular carcinoma

  • diffuse liver diseases, e.g. fatty infiltration, cirrhosis, hepatitis

  • biliary diseases, e.g. gallstones, cholecystitis

  • vascular abnormalities, e.g. portal hypertension, portal vein thrombosis

Some potential pitfalls and challenges that encounter during liver ultrasound include 3,4:

  • technical factors: such as shadowing artifacts from bowel gas or inappropriate gain settings

  • anatomic variations: e.g., accessory lobes or fissures that may mimic focal lesions

  • atypical appearances of benign hepatic lesions: e.g., complicated cysts or focal fatty sparing/replacement

  • small or isoechoic malignancies that may not be well visualized within the background parenchyma

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