Current diagnostic imaging modalities of the liver.

Although there are many complementary and supplementary types of diagnostic imaging of the liver, a logical sequence for most liver pathology begins with high-quality ultrasound. It is noninvasive and inexpensive but very operator dependent. In other settings, CT may be the preferable screening modality, as it gives an excellent picture of the global anatomy and is easily reproducible. Frequently, the two modalities are complementary and indicated; on other occasions, one method will suffice. Radionuclide evaluation of the liver is usually reserved for hepatobiliary imaging for biliary obstruction or the question of acute cholecystitis and tagged-red cell scanning for hemangioma. It is also frequently used for gallium scanning in hepatoma, but lymphoma and inflammatory diseases are also gallium avid. The invasive imaging tests of the liver--angiography and transhepatic and endoscopic retrograde cholangiography--are performed when insufficient information is obtained by the other methods (as in diagnostic transhepatic cholangiography) or when the procedure offers therapy (as for biliary drainage, percutaneous transhepatic removal of common bile duct stones, percutaneous cholecystosis with gallstone dissolution and liver embolization, or the angiographic evaluation for portal shunting or liver resection). The impact of magnetic resonance imaging and fourth-generation raid angiotomography CT scanning has yet to be felt. The use of intraoperative ultrasound is to be encouraged prior to liver resection because it can demonstrate lesions as small as 3 mm in diameter.