radiología en la red: Normal ultrasonographic anatomy of the liver

Estándar

  • Hepatic US is performed with standard curvilinear and high-resolution linear probes.
  • The curvilinear probe (2–6 MHz) allows acoustic penetration of deeper parenchyma while a high-resolution probe (7–12 MHz) may be used to depict greater surface detail.
  • Optimization of the gain, time-gain compensation, and tissue harmonics by an experienced sonologist, and second-look sonography by informed radiologists are requisites for achieving diagnostic examinations.
  • Normal liver parenchyma has a homogeneous echotexture, the assessment is subjective but the liver should not appear granular or coarsened if speckle reduction and compound imaging parameters are optimized.
  • Hepatic echogenicity is subjectively compared with that of adjacent solid viscera such as the kidneys and spleen; normal hepatic echogenicity is marginally higher than that of the kidney but less than that of the spleen.
  • The spleen provides a more reliable comparison because numerous intrinsic kidney diseases can alter their echogenicity.
  • Normal hepatic vessels have smooth walls and anechoic lumens.
  • Intrahepatic arteries are difficult to resolve on gray scale alone, but parallel the portal veins.
  • Normal spectral Doppler interrogation shows a low-resistance waveform with continuously hepatopetal diastolic flow.
  • Normal portal veins have thin echogenic walls and monophasic waveforms with mild respiratory variation. 
  • Alterations of portal mural echogenicity should be considered abnormal.
  • Normal hepatic veins and the inferior vena cava (IVC) lack discernible walls.
  • The normal hepatic venous waveform is triphasic, owing to 2 hepatofugal peaks and 1 hepatopetal peak reflecting primarily right atrial pressure.
  • The normal common bile duct measures up to 6 mm in normal individuals, but radiology dogma suggest that the diameter of the duct can increase with age.
  • The central intrahepatic ducts should normally measure 3 mm or less.
  • The diameter of the common bile duct may vary following cholecystectomy.
  • The normal perihepatic spaces should contain a variable amount of homogeneous fat; any ascites, fluid collection, or soft-tissue lesion should be considered abnormal.
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