Imaging of the liver, biliary system and pancreas - Investigations and procedures

Imaging of the liver, biliary system and pancreas

Plain abdominal X-ray

This is usually unhelpful, but occasionally abnormalities may be detected. Up to 10% of gallstones are radio-opaque and visible on X-ray. Pancreatic calcification may be seen in chronic pancreatitis. The finding of air in the biliary tree suggests infection with gas-producing organisms, trauma, a fistula between the intestine and gallbladder, or may be seen after endoscopic or surgical instrumentation.

Abdominal ultrasound scan (USS)

This is a safe, non-invasive test, which can be used to visualise the liver, biliary tree and pancreas. It is particularly useful in patients who have

·        jaundice or abnormal liver function tests where it is useful to look for gallstones, dilated intra- or extra-hepatic bile ducts, and to assess the size and appearance of the liver.

·        signs of chronic liver disease.

·        hepatomegaly or splenomegaly.

·        suspected gallstone disease, including cholecystitis.

·        acute pancreatitis, particularly to look for gallstones, pseudocysts and abscesses.

·        suspected intraabdominal abscess, e.g. liver abscess including amoebic abscess.

Other abnormal findings include ascites, abdominal masses and lymphadenopathy. Ultrasound may also be used for liver biopsy, and doppler ultrasound is used to look for hepatic blood flow, particularly portal vein flow direction and venous patency.

Computed tomography (CT)

This can visualise the liver, biliary tree, lymph nodes and the pancreas in more detail. Preferably a spiral CT is performed after intravenous contrast, as this allows imaging in the arterial and portal venous phases, which characterises liver lesions more precisely. Precautions should be taken in case of allergy or risk of contrast nephrotoxicity. This includes stopping metformin and ensuring patients are well-hydrated prior to the tests. CT is particularly useful for assessing focal lesions of the liver, staging of malignancy, and it is more sensitive for pancreatic lesions, such as assessing the severity of acute pancreatitis and to look for complications such as pseudocysts.

Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP)

This is sometimes used for more sensitive imaging of the liver, particularly for focal lesions. MRCP is some-times used as a noninvasive alternative to endoscopic retrograde cholangiopancreatography (ERCP) to visualise the pancreatic and biliary ducts, particularly in patients suspected of having biliary obstruction, stone or postliver transplant.