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Imaging in Hepatic Disease in Small Animals

By

Sharon A. Center

, BS, DVM, DACVIM, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University

Last full review/revision May 2015 | Content last modified May 2015

Radiography:

Routine abdominal radiographs are useful to determine liver size and may detect irregular liver borders. Mineralized densities that involve parenchyma or the biliary tree can reflect stasis of bile flow, dystrophic mineralization associated with congenital malformations, acquired duct “sacculation,” chronic duct inflammation, or choleliths. Choleliths that contain enough calcium bilirubinate or calcium carbonate are radiographically visible. A mass effect in the right cranial quadrant in suspected EHBDO may represent an engorged gallbladder, pancreatitis, neoplasia, or focal bile peritonitis. Radiographic suspicion of abdominal effusion (poor abdominal detail) may prompt diagnosis of bile peritonitis and ascitic effusion. Gas within hepatic parenchyma or biliary structures indicates an emphysematous process (eg, cholecystitis, choledochitis, infected biliary cyst, hepatic abscess, necrotic tumor mass) and warrants prompt antimicrobial therapy and either surgical intervention or percutaneous, ultrasound-guided aspiration/lavage. Thoracic radiography can indicate signs of systemic disease (eg, metastatic lesions, pleural fluid). Finding sternal lymphadenopathy is common in cats with the cholangitis/cholangiohepatitis syndrome, in which it reflects hepatic inflammation.

Although cholecystography can be accomplished with iodinated contrast given PO or IV, contrast radiographic imaging of the biliary system is rarely pursued. Distribution and concentration of contrast agents within biliary structures is influenced by numerous variables, including hyperbilirubinemia and major duct occlusion. At best, these agents may disclose choleliths, polyps, or sludged bile but are insufficient to confirm bile peritonitis or to localize the site of leakage. Multisector CT and/or hepatic ultrasonography are more useful to discern these processes.

Contrast studies of the portal vasculature are the gold standard for confirmation of a congenital portosystemic shunt. Radiographs should be taken in right and left lateral and ventrodorsal positions for best test sensitivity. Multisector CT imaging produces exceptional images and has replaced radiographic portography for diagnosis of congenital portosystemic shunts because it allows contrast injection into a peripheral vessel, can capture numerous images per second, and allows three-dimensional anatomic reconstruction.

Ultrasonography:

There are many diagnostic applications of hepatic ultrasonography: 1) identify distention and determine thickness of biliary structures; 2) verify common bile duct obstruction; 3) detect gallbladder mucoceles and cholelithiasis; 4) differentiate between diffuse and focal hepatic abnormalities; 5) identify and determine dimensions of “mass lesions”; 6) identify pancreatic, mesenteric, and perihepatic lymphadenomegaly; 7) in conjunction with vascular studies, identify congenital intrahepatic and extrahepatic portosystemic vascular anomalies (PSVAs), APSSs, arteriovenous malformations, and hepatic venule distention reflecting passive congestion; and 8) detect small volume abdominal effusion and small volume of fluid surrounding the gallbladder. However, although abdominal ultrasonography has become an indispensable diagnostic tool to assess the liver and biliary system, its use is highly operator dependent, and findings must always be reconciled with the history, physical examination findings, and clinicopathologic data. Reconciliation of data is best done by the principal clinician managing the case, who has the most knowledge of the animal's management and prognosis.

Computed Tomography:

Multisector CT imaging, available in specialty referral practices and university teaching hospitals, can distinguish mass lesions, detect changes in structure of hepatic parenchyma and the biliary system, identify choleliths, detect abnormal hepatic perfusion (involving the portal vein, hepatic artery, or hepatic vein), and portal thrombi, and can detail the extent of traumatic hepatobiliary injuries.

OTHER TOPICS IN THIS CHAPTER

Hepatic Disease in Small Animals
Overview of Hepatic Disease in Small Animals
Hematology in Hepatic Disease in Small Animals
Coagulation Tests in Hepatic Disease in Small Animals
Enzyme Activity in Hepatic Disease in Small Animals
Other Serum Biochemical Measures in Hepatic Disease in Small Animals
Hepatic Function Tests in Small Animals
Imaging in Hepatic Disease in Small Animals
Cholecystocentesis in Hepatic Disease in Small Animals
Liver Cytology in Small Animals
Liver Biopsy in Small Animals
Pathologic Changes in Bile in Small Animals
Nutrition in Hepatic Disease in Small Animals
Fulminant Hepatic Failure in Small Animals
Hepatic Encephalopathy in Small Animals
Portal Hypertension and Ascites in Small Animals
Portosystemic Vascular Malformations in Small Animals
Acquired Portosystemic Shunts in Small Animals
Other Hepatic Vascular Disorders in Small Animals
Hepatotoxins in Small Animals
Infectious Diseases of the Liver in Small Animals
Feline Hepatic Lipidosis
Biliary Cirrhosis in Small Animals
Canine Cholangiohepatitis
Canine Chronic Hepatitis
Lobular Dissecting Hepatitis in Small Animals
Canine Vacuolar Hepatopathy
Metabolic Diseases Affecting the Liver in Small Animals
Hepatocutaneous Syndrome in Small Animals
Nodular Hyperplasia in Small Animals
Hepatic Neoplasia in Small Animals
Miscellaneous Liver Diseases in Small Animals
Diseases of the Gallbladder and Extrahepatic Biliary System in Small Animals
Cholecystitis in Small Animals
Canine Gallbladder Mucocele
Other Disorders of the Gallbladder in Small Animals
Other Disorders of the Bile Ducts in Small Animals
Extrahepatic Bile Duct Obstruction in Small Animals
Cholelithiasis in Small Animals
Biliary Tree Rupture and Bile Peritonitis in Small Animals
Feline Cholangitis/Cholangiohepatitis Syndrome
Hepatobiliary Fluke Infection in Small Animals
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