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Imaging in Hepatobiliary Disease

Esther Barrett, MA, VetMB, DVDI, DECVDI, MRCVSt

Wales and West Imaging, Chepstow, UK

The aim of diagnostic imaging in hepatobiliary disease is As a result of this work, four main groups of liver disease
to provide information about the structure and, to a cer- have been established: parenchymal disorders, neoplas-
tain extent, the function of the hepatobiliary system. In tic disease, biliary tract disorders, and vascular disor-
common with the diagnostic imaging of all other organ ders. In this chapter, the WSAVA classification system is
systems, the imaging findings are rarely specific for a sin- used as a basis for describing the imaging features of
gle disease process and it is not possible to exclude dis- commonly encountered hepatobiliary diseases.
ease on the basis of apparently normal imaging findings.
Hepatobiliary imaging should therefore be considered Normal Hepatobiliary Anatomy
not as an isolated process but as an important part of the
overall diagnostic work‐up, with the imaging findings
always interpreted in the light of all the other available The canine and feline liver is the largest soft tissue organ
information (patient history, findings on physical exami- in the abdomen and is divided by deep fissures into left
nation, results of laboratory investigations, etc.). and right, quadrate and caudate lobes. The left and right
Radiography and ultrasonography are the techniques hepatic lobes are further divided into lateral and medial
most commonly used in the diagnostic imaging of the sublobes. The liver is located almost completely within
hepatobiliary system. Although much less widely availa- the costal arch, with a convex cranial surface lying imme-
ble, scintigraphy (nuclear medicine) is also a well‐estab- diately adjacent to the diaphragm and an irregularly con-
lished hepatobiliary imaging technique, useful in cave caudal surface lying in contact with the stomach,
providing functional as well as anatomic information. pancreas, duodenum, and right kidney. On the ventral
More recently, the advanced cross‐sectional imaging aspect of the liver, the proximal aspect of the fetal falci-
techniques of computed tomography (CT) and magnetic form ligament usually remains as an irregular fat‐filled
resonance imaging (MRI) have become increasingly use- fold (falciform fat).
ful, especially in the anatomic mapping of complicated
vascular anomalies and in the evaluation of, and poten- The Biliary System
tial surgical planning for, patients with liver masses.
The canine gallbladder is typically pear shaped and lies
between the quadrate and right medial lobes. The feline
gallbladder, which is sometimes folded or bilobed, usu-
Classification of Hepatobiliary Disease ally lies between two parts of the right medial lobe. The
common bile duct is formed by the confluence of the
In 2006, the WSAVA published the outcome of its hepatic cystic duct (from the gallbladder) with the hepatic duct/s
standardization project, an initiative started in July 2000 (directly from the liver). The common bile duct leaves
with the aim of describing universally accepted stand- the liver at the porta hepatis, where it lies ventral to the
ards and criteria for the diagnosis of all known liver dis- hepatic arteries and the hepatic portal vein, and enters
eases of dogs and cats. In establishing the recommended the proximal duodenum at the major duodenal papilla.
classification of different hepatobiliary diseases, ultra- In cats, the pancreatic duct usually joins the common
sonographic findings were considered an important fea- bile duct before emptying via the major duodenal papilla
ture, alongside clinical pathologic and histologic findings. into the proximal duodenum. In dogs, although both the

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical