Hepatobiliary imaging

Ultrasound is the primary modality for imaging of the liver and biliary system. CT and MR may also be used, but only if ultrasound does not visualise the pathology.

Magnetic resonance cholangiopancreatography (MCRP), endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography (PTC) are also used.

Indications

• Liver pathology
  • Hepatic tumour (HCC)
  • Liver abscess
  • Jaundice
  • Steatosis
  • Cirrhosis
• Biliary pathology
  • Gallstone disease
  • Cholecystitis
  • Cholangitis
  • Biliary stricture

Patient preparation

The patient should be fasting for 6 hours before. This is because the gallbladder contracts when eating, which makes visualisation of pathology in the gallbladder more difficult.

Interpretation

In a healthy person, the liver is isoechoic with the renal cortex, and the liver parenchyme is globally isoechoic. In case of steatosis, the liver is more echogenic (lighter on ultrasound) than the renal cortex. On CT, a steatotic liver will be less dense than the spleen.

Cholecystitis

Ultrasonographic signs of cholecystitis include thickened gallbladder wall, often with wall oedema, which makes it look like the gallbladder has a double wall.

Cirrhosis

In case of cirrhosis, some parts of the liver will be hyperechoic and some hypoechoic on ultrasound. The right lobe will be smaller than the left. On CT one can also see lobulation of the parenchyme and nodules in the liver.

Gall stone

Gall stones are visible on ultrasound as small structures that cast an acoustic shadow, as the ultrasounds cannot pass through the stone. If the stone is in the bile ducts (choledocholithiasis), the duct may be dilated proximally to the stone.