Ultrasonography of the liver and biliary tract.

Evaluation of the liver and biliary tract is one of the principal applications of abdominal ultrasonography in small animals. Indications include hepatomegaly, mass in the area of the liver, suspected hepatic metastasis, jaundice, ascites, suspected diaphragmatic rupture, and weight loss. Ultrasonography is a valuable method for evaluating the internal structure of the liver and biliary tract. Certain functional assessments also may be made, for example, measurement of induced gallbladder emptying after cholecystokinin injection. Limitations of ultrasonography include lack of specificity for focal or multifocal hepatic lesions and insensitivity for certain infiltrative diseases, such as lymphosarcoma. These limitations contribute to diagnostic difficulties, which are adequately addressed only by biopsy. The technique of ultrasound-guided biopsy is described briefly.